diff --git a/doc/sphinxext/numpy_ext/docscrape_sphinx.py b/doc/sphinxext/numpy_ext/docscrape_sphinx.py
index e44e770ef8..0f38188477 100644
--- a/doc/sphinxext/numpy_ext/docscrape_sphinx.py
+++ b/doc/sphinxext/numpy_ext/docscrape_sphinx.py
@@ -1,6 +1,7 @@
 import re, inspect, textwrap, pydoc
 import sphinx
 from docscrape import NumpyDocString, FunctionDoc, ClassDoc
+from nipype.external import six
 
 class SphinxDocString(NumpyDocString):
     def __init__(self, docstring, config={}):
@@ -140,7 +141,7 @@ def _str_references(self):
         out = []
         if self['References']:
             out += self._str_header('References')
-            if isinstance(self['References'], str):
+            if isinstance(self['References'], six.string_types):
                 self['References'] = [self['References']]
             out.extend(self['References'])
             out += ['']
diff --git a/examples/fmri_ants_openfmri.py b/examples/fmri_ants_openfmri.py
index 8af4603a1b..eab0ebe77b 100755
--- a/examples/fmri_ants_openfmri.py
+++ b/examples/fmri_ants_openfmri.py
@@ -14,6 +14,8 @@
 
 from nipype import config
 config.enable_provenance()
+from nipype.external import six
+
 
 from glob import glob
 import os
@@ -443,7 +445,7 @@ def get_contrasts(contrast_file, task_id, conds):
 
     def check_behav_list(behav):
         out_behav = []
-        if isinstance(behav, basestring):
+        if isinstance(behav, six.string_types):
             behav = [behav]
         for val in behav:
             if not isinstance(val, list):
diff --git a/examples/fmri_openfmri.py b/examples/fmri_openfmri.py
index 3f7ee4e424..174e55b96b 100755
--- a/examples/fmri_openfmri.py
+++ b/examples/fmri_openfmri.py
@@ -14,6 +14,7 @@
 
 from nipype import config
 config.enable_provenance()
+from nipype.external import six
 
 from glob import glob
 import os
@@ -237,7 +238,7 @@ def get_contrasts(contrast_file, task_id, conds):
 
     def check_behav_list(behav):
         out_behav = []
-        if isinstance(behav, basestring):
+        if isinstance(behav, six.string_types):
             behav = [behav]
         for val in behav:
             if not isinstance(val, list):
diff --git a/nipype/algorithms/modelgen.py b/nipype/algorithms/modelgen.py
index e763cc7538..19a2d5887f 100644
--- a/nipype/algorithms/modelgen.py
+++ b/nipype/algorithms/modelgen.py
@@ -30,6 +30,7 @@
                                     isdefined)
 from nipype.utils.filemanip import filename_to_list
 from .. import config, logging
+from nipype.external import six
 iflogger = logging.getLogger('interface')
 
 def gcd(a, b):
@@ -422,7 +423,7 @@ def _concatenate_info(self, infolist):
         for i, f in enumerate(self.inputs.functional_runs):
             if isinstance(f, list):
                 numscans = len(f)
-            elif isinstance(f, str):
+            elif isinstance(f, six.string_types):
                 img = load(f)
                 numscans = img.get_shape()[3]
             else:
diff --git a/nipype/algorithms/rapidart.py b/nipype/algorithms/rapidart.py
index 7b97352fdb..f304136d35 100644
--- a/nipype/algorithms/rapidart.py
+++ b/nipype/algorithms/rapidart.py
@@ -26,6 +26,7 @@
 import numpy as np
 from scipy import signal
 import scipy.io as sio
+from nipype.external import six
 
 from ..interfaces.base import (BaseInterface, traits, InputMultiPath,
                                     OutputMultiPath, TraitedSpec, File,
@@ -279,7 +280,7 @@ def _get_output_filenames(self, motionfile, output_dir):
         output_dir: string
             output directory in which the files will be generated
         """
-        if isinstance(motionfile, str):
+        if isinstance(motionfile, six.string_types):
             infile = motionfile
         elif isinstance(motionfile, list):
             infile = motionfile[0]
@@ -350,7 +351,7 @@ def _detect_outliers_core(self, imgfile, motionfile, runidx, cwd=None):
             cwd = os.getcwd()
 
         # read in functional image
-        if isinstance(imgfile, str):
+        if isinstance(imgfile, six.string_types):
             nim = load(imgfile)
         elif isinstance(imgfile, list):
             if len(imgfile) == 1:
diff --git a/nipype/external/provcopy.py b/nipype/external/provcopy.py
index 2f4900d1a9..59686f3b9b 100644
--- a/nipype/external/provcopy.py
+++ b/nipype/external/provcopy.py
@@ -17,6 +17,7 @@
 import dateutil.parser
 import collections
 from collections import defaultdict
+import six
 
 try:
     from rdflib.term import URIRef, BNode
@@ -187,7 +188,7 @@ def _parse_xsd_dateTime(s):
 
 
 def _ensure_datetime(time):
-    if isinstance(time, basestring):
+    if isinstance(time, six.string_types):
         return _parse_xsd_dateTime(time)
     else:
         return time
@@ -232,12 +233,12 @@ def parse_xsd_types(value, datatype):
 
 
 def _ensure_multiline_string_triple_quoted(s):
-    format_str = u'"""%s"""' if isinstance(s, basestring) and '\n' in s else u'"%s"'
+    format_str = u'"""%s"""' if isinstance(s, six.string_types) and '\n' in s else u'"%s"'
     return format_str % s
 
 
 def encoding_PROV_N_value(value):
-    if isinstance(value, basestring):
+    if isinstance(value, six.string_types):
         return _ensure_multiline_string_triple_quoted(value)
     elif isinstance(value, datetime.datetime):
         return value.isoformat()
@@ -536,7 +537,7 @@ def _auto_literal_conversion(self, literal):
         if isinstance(literal, URIRef):
             return literal
 
-        if isinstance(literal, basestring):
+        if isinstance(literal, six.string_types):
             return unicode(literal)
 
         if isinstance(literal, Literal) and literal.has_no_langtag():
@@ -1568,7 +1569,7 @@ def _decode_JSON_container(self, jc):
                          key=lambda tuple_rec: tuple_rec[0])
 
         record_map = {}
-        _parse_attr_value = lambda value: record_map[value] if (isinstance(value, basestring) and value in record_map) else self._decode_json_representation(value)
+        _parse_attr_value = lambda value: record_map[value] if (isinstance(value, six.string_types) and value in record_map) else self._decode_json_representation(value)
         #  Create all the records before setting their attributes
         for (record_type, identifier, content) in records:
             if record_type == PROV_REC_BUNDLE:
diff --git a/nipype/external/six.py b/nipype/external/six.py
new file mode 100644
index 0000000000..21b0e8032f
--- /dev/null
+++ b/nipype/external/six.py
@@ -0,0 +1,762 @@
+"""Utilities for writing code that runs on Python 2 and 3"""
+
+# Copyright (c) 2010-2014 Benjamin Peterson
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+from __future__ import absolute_import
+
+import functools
+import operator
+import sys
+import types
+
+__author__ = "Benjamin Peterson <benjamin@python.org>"
+__version__ = "1.8.0"
+
+
+# Useful for very coarse version differentiation.
+PY2 = sys.version_info[0] == 2
+PY3 = sys.version_info[0] == 3
+
+if PY3:
+    string_types = str,
+    integer_types = int,
+    class_types = type,
+    text_type = str
+    binary_type = bytes
+
+    MAXSIZE = sys.maxsize
+else:
+    string_types = basestring,
+    integer_types = (int, long)
+    class_types = (type, types.ClassType)
+    text_type = unicode
+    binary_type = str
+
+    if sys.platform.startswith("java"):
+        # Jython always uses 32 bits.
+        MAXSIZE = int((1 << 31) - 1)
+    else:
+        # It's possible to have sizeof(long) != sizeof(Py_ssize_t).
+        class X(object):
+            def __len__(self):
+                return 1 << 31
+        try:
+            len(X())
+        except OverflowError:
+            # 32-bit
+            MAXSIZE = int((1 << 31) - 1)
+        else:
+            # 64-bit
+            MAXSIZE = int((1 << 63) - 1)
+        del X
+
+
+def _add_doc(func, doc):
+    """Add documentation to a function."""
+    func.__doc__ = doc
+
+
+def _import_module(name):
+    """Import module, returning the module after the last dot."""
+    __import__(name)
+    return sys.modules[name]
+
+
+class _LazyDescr(object):
+
+    def __init__(self, name):
+        self.name = name
+
+    def __get__(self, obj, tp):
+        result = self._resolve()
+        setattr(obj, self.name, result) # Invokes __set__.
+        # This is a bit ugly, but it avoids running this again.
+        delattr(obj.__class__, self.name)
+        return result
+
+
+class MovedModule(_LazyDescr):
+
+    def __init__(self, name, old, new=None):
+        super(MovedModule, self).__init__(name)
+        if PY3:
+            if new is None:
+                new = name
+            self.mod = new
+        else:
+            self.mod = old
+
+    def _resolve(self):
+        return _import_module(self.mod)
+
+    def __getattr__(self, attr):
+        _module = self._resolve()
+        value = getattr(_module, attr)
+        setattr(self, attr, value)
+        return value
+
+
+class _LazyModule(types.ModuleType):
+
+    def __init__(self, name):
+        super(_LazyModule, self).__init__(name)
+        self.__doc__ = self.__class__.__doc__
+
+    def __dir__(self):
+        attrs = ["__doc__", "__name__"]
+        attrs += [attr.name for attr in self._moved_attributes]
+        return attrs
+
+    # Subclasses should override this
+    _moved_attributes = []
+
+
+class MovedAttribute(_LazyDescr):
+
+    def __init__(self, name, old_mod, new_mod, old_attr=None, new_attr=None):
+        super(MovedAttribute, self).__init__(name)
+        if PY3:
+            if new_mod is None:
+                new_mod = name
+            self.mod = new_mod
+            if new_attr is None:
+                if old_attr is None:
+                    new_attr = name
+                else:
+                    new_attr = old_attr
+            self.attr = new_attr
+        else:
+            self.mod = old_mod
+            if old_attr is None:
+                old_attr = name
+            self.attr = old_attr
+
+    def _resolve(self):
+        module = _import_module(self.mod)
+        return getattr(module, self.attr)
+
+
+class _SixMetaPathImporter(object):
+    """
+    A meta path importer to import six.moves and its submodules.
+
+    This class implements a PEP302 finder and loader. It should be compatible
+    with Python 2.5 and all existing versions of Python3
+    """
+    def __init__(self, six_module_name):
+        self.name = six_module_name
+        self.known_modules = {}
+
+    def _add_module(self, mod, *fullnames):
+        for fullname in fullnames:
+            self.known_modules[self.name + "." + fullname] = mod
+
+    def _get_module(self, fullname):
+        return self.known_modules[self.name + "." + fullname]
+
+    def find_module(self, fullname, path=None):
+        if fullname in self.known_modules:
+            return self
+        return None
+
+    def __get_module(self, fullname):
+        try:
+            return self.known_modules[fullname]
+        except KeyError:
+            raise ImportError("This loader does not know module " + fullname)
+
+    def load_module(self, fullname):
+        try:
+            # in case of a reload
+            return sys.modules[fullname]
+        except KeyError:
+            pass
+        mod = self.__get_module(fullname)
+        if isinstance(mod, MovedModule):
+            mod = mod._resolve()
+        else:
+            mod.__loader__ = self
+        sys.modules[fullname] = mod
+        return mod
+
+    def is_package(self, fullname):
+        """
+        Return true, if the named module is a package.
+
+        We need this method to get correct spec objects with
+        Python 3.4 (see PEP451)
+        """
+        return hasattr(self.__get_module(fullname), "__path__")
+
+    def get_code(self, fullname):
+        """Return None
+
+        Required, if is_package is implemented"""
+        self.__get_module(fullname)  # eventually raises ImportError
+        return None
+    get_source = get_code  # same as get_code
+
+_importer = _SixMetaPathImporter(__name__)
+
+
+class _MovedItems(_LazyModule):
+    """Lazy loading of moved objects"""
+    __path__ = []  # mark as package
+
+
+_moved_attributes = [
+    MovedAttribute("cStringIO", "cStringIO", "io", "StringIO"),
+    MovedAttribute("filter", "itertools", "builtins", "ifilter", "filter"),
+    MovedAttribute("filterfalse", "itertools", "itertools", "ifilterfalse", "filterfalse"),
+    MovedAttribute("input", "__builtin__", "builtins", "raw_input", "input"),
+    MovedAttribute("intern", "__builtin__", "sys"),
+    MovedAttribute("map", "itertools", "builtins", "imap", "map"),
+    MovedAttribute("range", "__builtin__", "builtins", "xrange", "range"),
+    MovedAttribute("reload_module", "__builtin__", "imp", "reload"),
+    MovedAttribute("reduce", "__builtin__", "functools"),
+    MovedAttribute("shlex_quote", "pipes", "shlex", "quote"),
+    MovedAttribute("StringIO", "StringIO", "io"),
+    MovedAttribute("UserDict", "UserDict", "collections"),
+    MovedAttribute("UserList", "UserList", "collections"),
+    MovedAttribute("UserString", "UserString", "collections"),
+    MovedAttribute("xrange", "__builtin__", "builtins", "xrange", "range"),
+    MovedAttribute("zip", "itertools", "builtins", "izip", "zip"),
+    MovedAttribute("zip_longest", "itertools", "itertools", "izip_longest", "zip_longest"),
+
+    MovedModule("builtins", "__builtin__"),
+    MovedModule("configparser", "ConfigParser"),
+    MovedModule("copyreg", "copy_reg"),
+    MovedModule("dbm_gnu", "gdbm", "dbm.gnu"),
+    MovedModule("_dummy_thread", "dummy_thread", "_dummy_thread"),
+    MovedModule("http_cookiejar", "cookielib", "http.cookiejar"),
+    MovedModule("http_cookies", "Cookie", "http.cookies"),
+    MovedModule("html_entities", "htmlentitydefs", "html.entities"),
+    MovedModule("html_parser", "HTMLParser", "html.parser"),
+    MovedModule("http_client", "httplib", "http.client"),
+    MovedModule("email_mime_multipart", "email.MIMEMultipart", "email.mime.multipart"),
+    MovedModule("email_mime_nonmultipart", "email.MIMENonMultipart", "email.mime.nonmultipart"),
+    MovedModule("email_mime_text", "email.MIMEText", "email.mime.text"),
+    MovedModule("email_mime_base", "email.MIMEBase", "email.mime.base"),
+    MovedModule("BaseHTTPServer", "BaseHTTPServer", "http.server"),
+    MovedModule("CGIHTTPServer", "CGIHTTPServer", "http.server"),
+    MovedModule("SimpleHTTPServer", "SimpleHTTPServer", "http.server"),
+    MovedModule("cPickle", "cPickle", "pickle"),
+    MovedModule("queue", "Queue"),
+    MovedModule("reprlib", "repr"),
+    MovedModule("socketserver", "SocketServer"),
+    MovedModule("_thread", "thread", "_thread"),
+    MovedModule("tkinter", "Tkinter"),
+    MovedModule("tkinter_dialog", "Dialog", "tkinter.dialog"),
+    MovedModule("tkinter_filedialog", "FileDialog", "tkinter.filedialog"),
+    MovedModule("tkinter_scrolledtext", "ScrolledText", "tkinter.scrolledtext"),
+    MovedModule("tkinter_simpledialog", "SimpleDialog", "tkinter.simpledialog"),
+    MovedModule("tkinter_tix", "Tix", "tkinter.tix"),
+    MovedModule("tkinter_ttk", "ttk", "tkinter.ttk"),
+    MovedModule("tkinter_constants", "Tkconstants", "tkinter.constants"),
+    MovedModule("tkinter_dnd", "Tkdnd", "tkinter.dnd"),
+    MovedModule("tkinter_colorchooser", "tkColorChooser",
+                "tkinter.colorchooser"),
+    MovedModule("tkinter_commondialog", "tkCommonDialog",
+                "tkinter.commondialog"),
+    MovedModule("tkinter_tkfiledialog", "tkFileDialog", "tkinter.filedialog"),
+    MovedModule("tkinter_font", "tkFont", "tkinter.font"),
+    MovedModule("tkinter_messagebox", "tkMessageBox", "tkinter.messagebox"),
+    MovedModule("tkinter_tksimpledialog", "tkSimpleDialog",
+                "tkinter.simpledialog"),
+    MovedModule("urllib_parse", __name__ + ".moves.urllib_parse", "urllib.parse"),
+    MovedModule("urllib_error", __name__ + ".moves.urllib_error", "urllib.error"),
+    MovedModule("urllib", __name__ + ".moves.urllib", __name__ + ".moves.urllib"),
+    MovedModule("urllib_robotparser", "robotparser", "urllib.robotparser"),
+    MovedModule("xmlrpc_client", "xmlrpclib", "xmlrpc.client"),
+    MovedModule("xmlrpc_server", "SimpleXMLRPCServer", "xmlrpc.server"),
+    MovedModule("winreg", "_winreg"),
+]
+for attr in _moved_attributes:
+    setattr(_MovedItems, attr.name, attr)
+    if isinstance(attr, MovedModule):
+        _importer._add_module(attr, "moves." + attr.name)
+del attr
+
+_MovedItems._moved_attributes = _moved_attributes
+
+moves = _MovedItems(__name__ + ".moves")
+_importer._add_module(moves, "moves")
+
+
+class Module_six_moves_urllib_parse(_LazyModule):
+    """Lazy loading of moved objects in six.moves.urllib_parse"""
+
+
+_urllib_parse_moved_attributes = [
+    MovedAttribute("ParseResult", "urlparse", "urllib.parse"),
+    MovedAttribute("SplitResult", "urlparse", "urllib.parse"),
+    MovedAttribute("parse_qs", "urlparse", "urllib.parse"),
+    MovedAttribute("parse_qsl", "urlparse", "urllib.parse"),
+    MovedAttribute("urldefrag", "urlparse", "urllib.parse"),
+    MovedAttribute("urljoin", "urlparse", "urllib.parse"),
+    MovedAttribute("urlparse", "urlparse", "urllib.parse"),
+    MovedAttribute("urlsplit", "urlparse", "urllib.parse"),
+    MovedAttribute("urlunparse", "urlparse", "urllib.parse"),
+    MovedAttribute("urlunsplit", "urlparse", "urllib.parse"),
+    MovedAttribute("quote", "urllib", "urllib.parse"),
+    MovedAttribute("quote_plus", "urllib", "urllib.parse"),
+    MovedAttribute("unquote", "urllib", "urllib.parse"),
+    MovedAttribute("unquote_plus", "urllib", "urllib.parse"),
+    MovedAttribute("urlencode", "urllib", "urllib.parse"),
+    MovedAttribute("splitquery", "urllib", "urllib.parse"),
+    MovedAttribute("splittag", "urllib", "urllib.parse"),
+    MovedAttribute("splituser", "urllib", "urllib.parse"),
+    MovedAttribute("uses_fragment", "urlparse", "urllib.parse"),
+    MovedAttribute("uses_netloc", "urlparse", "urllib.parse"),
+    MovedAttribute("uses_params", "urlparse", "urllib.parse"),
+    MovedAttribute("uses_query", "urlparse", "urllib.parse"),
+    MovedAttribute("uses_relative", "urlparse", "urllib.parse"),
+]
+for attr in _urllib_parse_moved_attributes:
+    setattr(Module_six_moves_urllib_parse, attr.name, attr)
+del attr
+
+Module_six_moves_urllib_parse._moved_attributes = _urllib_parse_moved_attributes
+
+_importer._add_module(Module_six_moves_urllib_parse(__name__ + ".moves.urllib_parse"),
+                      "moves.urllib_parse", "moves.urllib.parse")
+
+
+class Module_six_moves_urllib_error(_LazyModule):
+    """Lazy loading of moved objects in six.moves.urllib_error"""
+
+
+_urllib_error_moved_attributes = [
+    MovedAttribute("URLError", "urllib2", "urllib.error"),
+    MovedAttribute("HTTPError", "urllib2", "urllib.error"),
+    MovedAttribute("ContentTooShortError", "urllib", "urllib.error"),
+]
+for attr in _urllib_error_moved_attributes:
+    setattr(Module_six_moves_urllib_error, attr.name, attr)
+del attr
+
+Module_six_moves_urllib_error._moved_attributes = _urllib_error_moved_attributes
+
+_importer._add_module(Module_six_moves_urllib_error(__name__ + ".moves.urllib.error"),
+                      "moves.urllib_error", "moves.urllib.error")
+
+
+class Module_six_moves_urllib_request(_LazyModule):
+    """Lazy loading of moved objects in six.moves.urllib_request"""
+
+
+_urllib_request_moved_attributes = [
+    MovedAttribute("urlopen", "urllib2", "urllib.request"),
+    MovedAttribute("install_opener", "urllib2", "urllib.request"),
+    MovedAttribute("build_opener", "urllib2", "urllib.request"),
+    MovedAttribute("pathname2url", "urllib", "urllib.request"),
+    MovedAttribute("url2pathname", "urllib", "urllib.request"),
+    MovedAttribute("getproxies", "urllib", "urllib.request"),
+    MovedAttribute("Request", "urllib2", "urllib.request"),
+    MovedAttribute("OpenerDirector", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPDefaultErrorHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPRedirectHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPCookieProcessor", "urllib2", "urllib.request"),
+    MovedAttribute("ProxyHandler", "urllib2", "urllib.request"),
+    MovedAttribute("BaseHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPPasswordMgr", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPPasswordMgrWithDefaultRealm", "urllib2", "urllib.request"),
+    MovedAttribute("AbstractBasicAuthHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPBasicAuthHandler", "urllib2", "urllib.request"),
+    MovedAttribute("ProxyBasicAuthHandler", "urllib2", "urllib.request"),
+    MovedAttribute("AbstractDigestAuthHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPDigestAuthHandler", "urllib2", "urllib.request"),
+    MovedAttribute("ProxyDigestAuthHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPSHandler", "urllib2", "urllib.request"),
+    MovedAttribute("FileHandler", "urllib2", "urllib.request"),
+    MovedAttribute("FTPHandler", "urllib2", "urllib.request"),
+    MovedAttribute("CacheFTPHandler", "urllib2", "urllib.request"),
+    MovedAttribute("UnknownHandler", "urllib2", "urllib.request"),
+    MovedAttribute("HTTPErrorProcessor", "urllib2", "urllib.request"),
+    MovedAttribute("urlretrieve", "urllib", "urllib.request"),
+    MovedAttribute("urlcleanup", "urllib", "urllib.request"),
+    MovedAttribute("URLopener", "urllib", "urllib.request"),
+    MovedAttribute("FancyURLopener", "urllib", "urllib.request"),
+    MovedAttribute("proxy_bypass", "urllib", "urllib.request"),
+]
+for attr in _urllib_request_moved_attributes:
+    setattr(Module_six_moves_urllib_request, attr.name, attr)
+del attr
+
+Module_six_moves_urllib_request._moved_attributes = _urllib_request_moved_attributes
+
+_importer._add_module(Module_six_moves_urllib_request(__name__ + ".moves.urllib.request"),
+                      "moves.urllib_request", "moves.urllib.request")
+
+
+class Module_six_moves_urllib_response(_LazyModule):
+    """Lazy loading of moved objects in six.moves.urllib_response"""
+
+
+_urllib_response_moved_attributes = [
+    MovedAttribute("addbase", "urllib", "urllib.response"),
+    MovedAttribute("addclosehook", "urllib", "urllib.response"),
+    MovedAttribute("addinfo", "urllib", "urllib.response"),
+    MovedAttribute("addinfourl", "urllib", "urllib.response"),
+]
+for attr in _urllib_response_moved_attributes:
+    setattr(Module_six_moves_urllib_response, attr.name, attr)
+del attr
+
+Module_six_moves_urllib_response._moved_attributes = _urllib_response_moved_attributes
+
+_importer._add_module(Module_six_moves_urllib_response(__name__ + ".moves.urllib.response"),
+                      "moves.urllib_response", "moves.urllib.response")
+
+
+class Module_six_moves_urllib_robotparser(_LazyModule):
+    """Lazy loading of moved objects in six.moves.urllib_robotparser"""
+
+
+_urllib_robotparser_moved_attributes = [
+    MovedAttribute("RobotFileParser", "robotparser", "urllib.robotparser"),
+]
+for attr in _urllib_robotparser_moved_attributes:
+    setattr(Module_six_moves_urllib_robotparser, attr.name, attr)
+del attr
+
+Module_six_moves_urllib_robotparser._moved_attributes = _urllib_robotparser_moved_attributes
+
+_importer._add_module(Module_six_moves_urllib_robotparser(__name__ + ".moves.urllib.robotparser"),
+                      "moves.urllib_robotparser", "moves.urllib.robotparser")
+
+
+class Module_six_moves_urllib(types.ModuleType):
+    """Create a six.moves.urllib namespace that resembles the Python 3 namespace"""
+    __path__ = []  # mark as package
+    parse = _importer._get_module("moves.urllib_parse")
+    error = _importer._get_module("moves.urllib_error")
+    request = _importer._get_module("moves.urllib_request")
+    response = _importer._get_module("moves.urllib_response")
+    robotparser = _importer._get_module("moves.urllib_robotparser")
+
+    def __dir__(self):
+        return ['parse', 'error', 'request', 'response', 'robotparser']
+
+_importer._add_module(Module_six_moves_urllib(__name__ + ".moves.urllib"),
+                      "moves.urllib")
+
+
+def add_move(move):
+    """Add an item to six.moves."""
+    setattr(_MovedItems, move.name, move)
+
+
+def remove_move(name):
+    """Remove item from six.moves."""
+    try:
+        delattr(_MovedItems, name)
+    except AttributeError:
+        try:
+            del moves.__dict__[name]
+        except KeyError:
+            raise AttributeError("no such move, %r" % (name,))
+
+
+if PY3:
+    _meth_func = "__func__"
+    _meth_self = "__self__"
+
+    _func_closure = "__closure__"
+    _func_code = "__code__"
+    _func_defaults = "__defaults__"
+    _func_globals = "__globals__"
+else:
+    _meth_func = "im_func"
+    _meth_self = "im_self"
+
+    _func_closure = "func_closure"
+    _func_code = "func_code"
+    _func_defaults = "func_defaults"
+    _func_globals = "func_globals"
+
+
+try:
+    advance_iterator = next
+except NameError:
+    def advance_iterator(it):
+        return it.next()
+next = advance_iterator
+
+
+try:
+    callable = callable
+except NameError:
+    def callable(obj):
+        return any("__call__" in klass.__dict__ for klass in type(obj).__mro__)
+
+
+if PY3:
+    def get_unbound_function(unbound):
+        return unbound
+
+    create_bound_method = types.MethodType
+
+    Iterator = object
+else:
+    def get_unbound_function(unbound):
+        return unbound.im_func
+
+    def create_bound_method(func, obj):
+        return types.MethodType(func, obj, obj.__class__)
+
+    class Iterator(object):
+
+        def next(self):
+            return type(self).__next__(self)
+
+    callable = callable
+_add_doc(get_unbound_function,
+         """Get the function out of a possibly unbound function""")
+
+
+get_method_function = operator.attrgetter(_meth_func)
+get_method_self = operator.attrgetter(_meth_self)
+get_function_closure = operator.attrgetter(_func_closure)
+get_function_code = operator.attrgetter(_func_code)
+get_function_defaults = operator.attrgetter(_func_defaults)
+get_function_globals = operator.attrgetter(_func_globals)
+
+
+if PY3:
+    def iterkeys(d, **kw):
+        return iter(d.keys(**kw))
+
+    def itervalues(d, **kw):
+        return iter(d.values(**kw))
+
+    def iteritems(d, **kw):
+        return iter(d.items(**kw))
+
+    def iterlists(d, **kw):
+        return iter(d.lists(**kw))
+else:
+    def iterkeys(d, **kw):
+        return iter(d.iterkeys(**kw))
+
+    def itervalues(d, **kw):
+        return iter(d.itervalues(**kw))
+
+    def iteritems(d, **kw):
+        return iter(d.iteritems(**kw))
+
+    def iterlists(d, **kw):
+        return iter(d.iterlists(**kw))
+
+_add_doc(iterkeys, "Return an iterator over the keys of a dictionary.")
+_add_doc(itervalues, "Return an iterator over the values of a dictionary.")
+_add_doc(iteritems,
+         "Return an iterator over the (key, value) pairs of a dictionary.")
+_add_doc(iterlists,
+         "Return an iterator over the (key, [values]) pairs of a dictionary.")
+
+
+if PY3:
+    def b(s):
+        return s.encode("latin-1")
+    def u(s):
+        return s
+    unichr = chr
+    if sys.version_info[1] <= 1:
+        def int2byte(i):
+            return bytes((i,))
+    else:
+        # This is about 2x faster than the implementation above on 3.2+
+        int2byte = operator.methodcaller("to_bytes", 1, "big")
+    byte2int = operator.itemgetter(0)
+    indexbytes = operator.getitem
+    iterbytes = iter
+    import io
+    StringIO = io.StringIO
+    BytesIO = io.BytesIO
+else:
+    def b(s):
+        return s
+    # Workaround for standalone backslash
+    def u(s):
+        return unicode(s.replace(r'\\', r'\\\\'), "unicode_escape")
+    unichr = unichr
+    int2byte = chr
+    def byte2int(bs):
+        return ord(bs[0])
+    def indexbytes(buf, i):
+        return ord(buf[i])
+    def iterbytes(buf):
+        return (ord(byte) for byte in buf)
+    import StringIO
+    StringIO = BytesIO = StringIO.StringIO
+_add_doc(b, """Byte literal""")
+_add_doc(u, """Text literal""")
+
+
+if PY3:
+    exec_ = getattr(moves.builtins, "exec")
+
+
+    def reraise(tp, value, tb=None):
+        if value is None:
+            value = tp()
+        if value.__traceback__ is not tb:
+            raise value.with_traceback(tb)
+        raise value
+
+else:
+    def exec_(_code_, _globs_=None, _locs_=None):
+        """Execute code in a namespace."""
+        if _globs_ is None:
+            frame = sys._getframe(1)
+            _globs_ = frame.f_globals
+            if _locs_ is None:
+                _locs_ = frame.f_locals
+            del frame
+        elif _locs_ is None:
+            _locs_ = _globs_
+        exec("""exec _code_ in _globs_, _locs_""")
+
+
+    exec_("""def reraise(tp, value, tb=None):
+    raise tp, value, tb
+""")
+
+
+print_ = getattr(moves.builtins, "print", None)
+if print_ is None:
+    def print_(*args, **kwargs):
+        """The new-style print function for Python 2.4 and 2.5."""
+        fp = kwargs.pop("file", sys.stdout)
+        if fp is None:
+            return
+        def write(data):
+            if not isinstance(data, basestring):
+                data = str(data)
+            # If the file has an encoding, encode unicode with it.
+            if (isinstance(fp, file) and
+                isinstance(data, unicode) and
+                fp.encoding is not None):
+                errors = getattr(fp, "errors", None)
+                if errors is None:
+                    errors = "strict"
+                data = data.encode(fp.encoding, errors)
+            fp.write(data)
+        want_unicode = False
+        sep = kwargs.pop("sep", None)
+        if sep is not None:
+            if isinstance(sep, unicode):
+                want_unicode = True
+            elif not isinstance(sep, str):
+                raise TypeError("sep must be None or a string")
+        end = kwargs.pop("end", None)
+        if end is not None:
+            if isinstance(end, unicode):
+                want_unicode = True
+            elif not isinstance(end, str):
+                raise TypeError("end must be None or a string")
+        if kwargs:
+            raise TypeError("invalid keyword arguments to print()")
+        if not want_unicode:
+            for arg in args:
+                if isinstance(arg, unicode):
+                    want_unicode = True
+                    break
+        if want_unicode:
+            newline = unicode("\n")
+            space = unicode(" ")
+        else:
+            newline = "\n"
+            space = " "
+        if sep is None:
+            sep = space
+        if end is None:
+            end = newline
+        for i, arg in enumerate(args):
+            if i:
+                write(sep)
+            write(arg)
+        write(end)
+
+_add_doc(reraise, """Reraise an exception.""")
+
+if sys.version_info[0:2] < (3, 4):
+    def wraps(wrapped, assigned=functools.WRAPPER_ASSIGNMENTS,
+              updated=functools.WRAPPER_UPDATES):
+        def wrapper(f):
+            f = functools.wraps(wrapped)(f)
+            f.__wrapped__ = wrapped
+            return f
+        return wrapper
+else:
+    wraps = functools.wraps
+
+def with_metaclass(meta, *bases):
+    """Create a base class with a metaclass."""
+    # This requires a bit of explanation: the basic idea is to make a dummy
+    # metaclass for one level of class instantiation that replaces itself with
+    # the actual metaclass.
+    class metaclass(meta):
+        def __new__(cls, name, this_bases, d):
+            return meta(name, bases, d)
+    return type.__new__(metaclass, 'temporary_class', (), {})
+
+
+def add_metaclass(metaclass):
+    """Class decorator for creating a class with a metaclass."""
+    def wrapper(cls):
+        orig_vars = cls.__dict__.copy()
+        slots = orig_vars.get('__slots__')
+        if slots is not None:
+            if isinstance(slots, str):
+                slots = [slots]
+            for slots_var in slots:
+                orig_vars.pop(slots_var)
+        orig_vars.pop('__dict__', None)
+        orig_vars.pop('__weakref__', None)
+        return metaclass(cls.__name__, cls.__bases__, orig_vars)
+    return wrapper
+
+# Complete the moves implementation.
+# This code is at the end of this module to speed up module loading.
+# Turn this module into a package.
+__path__ = []  # required for PEP 302 and PEP 451
+__package__ = __name__  # see PEP 366 @ReservedAssignment
+if globals().get("__spec__") is not None:
+    __spec__.submodule_search_locations = []  # PEP 451 @UndefinedVariable
+# Remove other six meta path importers, since they cause problems. This can
+# happen if six is removed from sys.modules and then reloaded. (Setuptools does
+# this for some reason.)
+if sys.meta_path:
+    for i, importer in enumerate(sys.meta_path):
+        # Here's some real nastiness: Another "instance" of the six module might
+        # be floating around. Therefore, we can't use isinstance() to check for
+        # the six meta path importer, since the other six instance will have
+        # inserted an importer with different class.
+        if (type(importer).__name__ == "_SixMetaPathImporter" and
+            importer.name == __name__):
+            del sys.meta_path[i]
+            break
+    del i, importer
+# Finally, add the importer to the meta path import hook.
+sys.meta_path.append(_importer)
diff --git a/nipype/fixes/numpy/testing/nosetester.py b/nipype/fixes/numpy/testing/nosetester.py
index d6df51b0c7..735a5be749 100644
--- a/nipype/fixes/numpy/testing/nosetester.py
+++ b/nipype/fixes/numpy/testing/nosetester.py
@@ -6,6 +6,7 @@
 """
 import os
 import sys
+from nipype.external import six
 
 def get_package_name(filepath):
     """
@@ -166,7 +167,7 @@ def _test_argv(self, label, verbose, extra_argv):
         '''
         argv = [__file__, self.package_path, '-s']
         if label and label != 'full':
-            if not isinstance(label, basestring):
+            if not isinstance(label, six.string_types):
                 raise TypeError('Selection label should be a string')
             if label == 'fast':
                 label = 'not slow'
diff --git a/nipype/interfaces/base.py b/nipype/interfaces/base.py
index c244998958..ef6f8fd1a1 100644
--- a/nipype/interfaces/base.py
+++ b/nipype/interfaces/base.py
@@ -24,6 +24,7 @@
 from datetime import datetime as dt
 from dateutil.parser import parse as parseutc
 from warnings import warn
+from nipype.external import six
 
 
 from .traits_extension import (traits, Undefined, TraitDictObject,
@@ -541,7 +542,7 @@ def _get_sorteddict(self, object, dictwithhash=False, hash_method=None,
                 out = tuple(out)
         else:
             if isdefined(object):
-                if (hash_files and isinstance(object, str) and
+                if (hash_files and isinstance(object, six.string_types) and
                         os.path.isfile(object)):
                     if hash_method is None:
                         hash_method = config.get('execution', 'hash_method')
@@ -984,7 +985,7 @@ def run(self, **inputs):
             else:
                 inputs_str = ''
 
-            if len(e.args) == 1 and isinstance(e.args[0], str):
+            if len(e.args) == 1 and isinstance(e.args[0], six.string_types):
                 e.args = (e.args[0] + " ".join([message, inputs_str]),)
             else:
                 e.args += (message, )
diff --git a/nipype/interfaces/dcmstack.py b/nipype/interfaces/dcmstack.py
index d6a4b13580..1223ec7623 100644
--- a/nipype/interfaces/dcmstack.py
+++ b/nipype/interfaces/dcmstack.py
@@ -23,6 +23,7 @@
 import nibabel as nb
 from nipype.interfaces.traits_extension import isdefined, Undefined
 import imghdr
+from nipype.external import six
 
 have_dcmstack = True
 try:
@@ -109,7 +110,7 @@ class DcmStack(NiftiGeneratorBase):
     output_spec = DcmStackOutputSpec
 
     def _get_filelist(self, trait_input):
-        if isinstance(trait_input, str):
+        if isinstance(trait_input, six.string_types):
             if path.isdir(trait_input):
                 return glob(path.join(trait_input, '*.dcm'))
             else:
@@ -334,7 +335,7 @@ def _run_interface(self, runtime):
               ]
         if self.inputs.sort_order:
             sort_order = self.inputs.sort_order
-            if isinstance(sort_order, str):
+            if isinstance(sort_order, six.string_types):
                 sort_order = [sort_order]
             nws.sort(key=make_key_func(sort_order))
         if self.inputs.merge_dim == traits.Undefined:
diff --git a/nipype/interfaces/io.py b/nipype/interfaces/io.py
index 675c90e98d..dc694cd94b 100644
--- a/nipype/interfaces/io.py
+++ b/nipype/interfaces/io.py
@@ -30,6 +30,7 @@
 
 import sqlite3
 from nipype.utils.misc import human_order_sorted
+from nipype.external import six
 
 try:
     import pyxnat
@@ -520,7 +521,7 @@ def _list_outputs(self):
             for argnum, arglist in enumerate(args):
                 maxlen = 1
                 for arg in arglist:
-                    if isinstance(arg, str) and hasattr(self.inputs, arg):
+                    if isinstance(arg, six.string_types) and hasattr(self.inputs, arg):
                         arg = getattr(self.inputs, arg)
                     if isinstance(arg, list):
                         if (maxlen > 1) and (len(arg) != maxlen):
@@ -531,7 +532,7 @@ def _list_outputs(self):
                 for i in range(maxlen):
                     argtuple = []
                     for arg in arglist:
-                        if isinstance(arg, str) and hasattr(self.inputs, arg):
+                        if isinstance(arg, six.string_types) and hasattr(self.inputs, arg):
                             arg = getattr(self.inputs, arg)
                         if isinstance(arg, list):
                             argtuple.append(arg[i])
@@ -786,7 +787,7 @@ def _match_path(self, target_path):
 
     def _run_interface(self, runtime):
         #Prepare some of the inputs
-        if isinstance(self.inputs.root_paths, str):
+        if isinstance(self.inputs.root_paths, six.string_types):
             self.inputs.root_paths = [self.inputs.root_paths]
         self.match_regex = re.compile(self.inputs.match_regex)
         if self.inputs.max_depth is Undefined:
@@ -1155,7 +1156,7 @@ def _list_outputs(self):
             for argnum, arglist in enumerate(args):
                 maxlen = 1
                 for arg in arglist:
-                    if isinstance(arg, str) and hasattr(self.inputs, arg):
+                    if isinstance(arg, six.string_types) and hasattr(self.inputs, arg):
                         arg = getattr(self.inputs, arg)
                     if isinstance(arg, list):
                         if (maxlen > 1) and (len(arg) != maxlen):
@@ -1168,7 +1169,7 @@ def _list_outputs(self):
                 for i in range(maxlen):
                     argtuple = []
                     for arg in arglist:
-                        if isinstance(arg, str) and \
+                        if isinstance(arg, six.string_types) and \
                                 hasattr(self.inputs, arg):
                             arg = getattr(self.inputs, arg)
                         if isinstance(arg, list):
@@ -1725,7 +1726,7 @@ def _list_outputs(self):
             for argnum, arglist in enumerate(args):
                 maxlen = 1
                 for arg in arglist:
-                    if isinstance(arg, str) and hasattr(self.inputs, arg):
+                    if isinstance(arg, six.string_types) and hasattr(self.inputs, arg):
                         arg = getattr(self.inputs, arg)
                     if isinstance(arg, list):
                         if (maxlen > 1) and (len(arg) != maxlen):
@@ -1736,7 +1737,7 @@ def _list_outputs(self):
                 for i in range(maxlen):
                     argtuple = []
                     for arg in arglist:
-                        if isinstance(arg, str) and hasattr(self.inputs, arg):
+                        if isinstance(arg, six.string_types) and hasattr(self.inputs, arg):
                             arg = getattr(self.inputs, arg)
                         if isinstance(arg, list):
                             argtuple.append(arg[i])
diff --git a/nipype/interfaces/mne/base.py b/nipype/interfaces/mne/base.py
index 67beb888b2..609dcd2246 100644
--- a/nipype/interfaces/mne/base.py
+++ b/nipype/interfaces/mne/base.py
@@ -4,6 +4,7 @@
 import glob
 from nipype.interfaces.freesurfer.base import FSCommand, FSTraitedSpec
 from nipype.utils.filemanip import list_to_filename
+from nipype.external import six
 import logging
 
 logging.basicConfig()
@@ -89,7 +90,7 @@ def _list_outputs(self):
                         out_files = []
                         for value in value_list:
                             out_files.append(op.abspath(value))
-                    elif isinstance(value_list, str):
+                    elif isinstance(value_list, six.string_types):
                         out_files = op.abspath(value_list)
                     else:
                         raise TypeError
diff --git a/nipype/interfaces/nipy/model.py b/nipype/interfaces/nipy/model.py
index 76b583b355..ebbe394fdc 100644
--- a/nipype/interfaces/nipy/model.py
+++ b/nipype/interfaces/nipy/model.py
@@ -3,6 +3,7 @@
 
 import nibabel as nb
 import numpy as np
+from nipype.external import six
 
 
 from ...utils.misc import package_check
@@ -80,7 +81,7 @@ def _run_interface(self, runtime):
         session_info = self.inputs.session_info
 
         functional_runs = self.inputs.session_info[0]['scans']
-        if isinstance(functional_runs, str):
+        if isinstance(functional_runs, six.string_types):
             functional_runs = [functional_runs]
         nii = nb.load(functional_runs[0])
         data = nii.get_data()
diff --git a/nipype/interfaces/slicer/generate_classes.py b/nipype/interfaces/slicer/generate_classes.py
index 4affadafc5..013f31c75c 100644
--- a/nipype/interfaces/slicer/generate_classes.py
+++ b/nipype/interfaces/slicer/generate_classes.py
@@ -7,6 +7,7 @@
 import subprocess
 import os
 from shutil import rmtree
+from nipype.external import six
 
 import keyword
 python_keywords = keyword.kwlist  # If c++ SEM module uses one of these key words as a command line parameter, we need to modify variable
@@ -47,7 +48,7 @@ def add_class_to_package(class_codes, class_names, module_name, package_dir):
 def crawl_code_struct(code_struct, package_dir):
     subpackages = []
     for k, v in code_struct.iteritems():
-        if isinstance(v, str) or isinstance(v, unicode):
+        if isinstance(v, six.string_types) or isinstance(v, unicode):
             module_name = k.lower()
             class_name = k
             class_code = v
@@ -57,7 +58,7 @@ def crawl_code_struct(code_struct, package_dir):
             l1 = {}
             l2 = {}
             for key in v.keys():
-                if (isinstance(v[key], str) or isinstance(v[key], unicode)):
+                if (isinstance(v[key], six.string_types) or isinstance(v[key], unicode)):
                     l1[key] = v[key]
                 else:
                     l2[key] = v[key]
@@ -313,7 +314,7 @@ def grab_xml(module, launcher):
 def parse_params(params):
     list = []
     for key, value in params.iteritems():
-        if isinstance(value, str) or isinstance(value, unicode):
+        if isinstance(value, six.string_types) or isinstance(value, unicode):
             list.append('%s="%s"' % (key, value.replace('"', "'")))
         else:
             list.append('%s=%s' % (key, value))
diff --git a/nipype/interfaces/spm/base.py b/nipype/interfaces/spm/base.py
index c47abf0a6d..6d0ea0eb50 100644
--- a/nipype/interfaces/spm/base.py
+++ b/nipype/interfaces/spm/base.py
@@ -24,6 +24,7 @@
 from nibabel import load
 import numpy as np
 from scipy.io import savemat
+from nipype.external import six
 
 # Local imports
 from ..base import (BaseInterface, traits, isdefined, InputMultiPath,
@@ -416,7 +417,7 @@ def _generate_job(self, prefix='', contents=None):
                     if isinstance(val, np.ndarray):
                         jobstring += self._generate_job(prefix=None,
                                                         contents=val)
-                    elif isinstance(val, str):
+                    elif isinstance(val, six.string_types):
                         jobstring += '\'%s\';...\n' % (val)
                     else:
                         jobstring += '%s;...\n' % str(val)
@@ -431,7 +432,7 @@ def _generate_job(self, prefix='', contents=None):
                         jobstring += self._generate_job(newprefix,
                                                         val[field])
             return jobstring
-        if isinstance(contents, str):
+        if isinstance(contents, six.string_types):
             jobstring += "%s = '%s';\n" % (prefix, contents)
             return jobstring
         jobstring += "%s = %s;\n" % (prefix, str(contents))
diff --git a/nipype/interfaces/spm/model.py b/nipype/interfaces/spm/model.py
index 5b0528a084..eddf3ec47a 100644
--- a/nipype/interfaces/spm/model.py
+++ b/nipype/interfaces/spm/model.py
@@ -20,6 +20,7 @@
 # Third-party imports
 import numpy as np
 import scipy.io as sio
+from nipype.external import six
 
 # Local imports
 from nipype.interfaces.base import (Bunch, traits, TraitedSpec, File, Directory,
@@ -196,7 +197,7 @@ def _format_arg(self, opt, spec, val):
         if opt == 'spm_mat_file':
             return np.array([str(val)], dtype=object)
         if opt == 'estimation_method':
-            if isinstance(val, str):
+            if isinstance(val, six.string_types):
                 return {'%s' % val: 1}
             else:
                 return val
diff --git a/nipype/interfaces/utility.py b/nipype/interfaces/utility.py
index 005eb4a501..210d74e134 100644
--- a/nipype/interfaces/utility.py
+++ b/nipype/interfaces/utility.py
@@ -5,6 +5,7 @@
 from cPickle import dumps, loads
 import numpy as np
 import nibabel as nb
+from nipype.external import six
 
 from nipype.utils.filemanip import (filename_to_list, copyfile, split_filename)
 from nipype.interfaces.base import (traits, TraitedSpec, DynamicTraitedSpec, File,
@@ -386,7 +387,7 @@ def __init__(self, input_names, output_names, function=None, imports=None,
                     raise Exception('Interface Function does not accept ' \
                                     'function objects defined interactively ' \
                                     'in a python session')
-            elif isinstance(function, str):
+            elif isinstance(function, six.string_types):
                 self.inputs.function_str = dumps(function)
             else:
                 raise Exception('Unknown type of function')
@@ -404,7 +405,7 @@ def _set_function_string(self, obj, name, old, new):
         if name == 'function_str':
             if hasattr(new, '__call__'):
                 function_source = getsource(new)
-            elif isinstance(new, str):
+            elif isinstance(new, six.string_types):
                 function_source = dumps(new)
             self.inputs.trait_set(trait_change_notify=False,
                                   **{'%s' % name: function_source})
diff --git a/nipype/pipeline/engine.py b/nipype/pipeline/engine.py
index 5e403ac22d..ea31ca8378 100644
--- a/nipype/pipeline/engine.py
+++ b/nipype/pipeline/engine.py
@@ -34,6 +34,7 @@
 from tempfile import mkdtemp
 from warnings import warn
 from hashlib import sha1
+from nipype.external import six
 
 import numpy as np
 
@@ -361,7 +362,7 @@ def connect(self, *args, **kwargs):
                         # handles the case that source is specified
                         # with a function
                         sourcename = source[0]
-                    elif isinstance(source, str):
+                    elif isinstance(source, six.string_types):
                         sourcename = source
                     else:
                         raise Exception(('Unknown source specification in '
@@ -382,7 +383,7 @@ def connect(self, *args, **kwargs):
         # turn functions into strings
         for srcnode, destnode, connects in connection_list:
             for idx, (src, dest) in enumerate(connects):
-                if isinstance(src, tuple) and not isinstance(src[1], str):
+                if isinstance(src, tuple) and not isinstance(src[1], six.string_types):
                     function_source = getsource(src[1])
                     connects[idx] = ((src[0], function_source, src[2:]), dest)
 
@@ -896,7 +897,7 @@ def _set_input(self, object, name, newvalue):
 
     def _set_node_input(self, node, param, source, sourceinfo):
         """Set inputs of a node given the edge connection"""
-        if isinstance(sourceinfo, str):
+        if isinstance(sourceinfo, six.string_types):
             val = source.get_output(sourceinfo)
         elif isinstance(sourceinfo, tuple):
             if callable(sourceinfo[1]):
@@ -1841,7 +1842,7 @@ def __init__(self, interface, name, joinsource, joinfield=None,
         if not joinfield:
             # default is the interface fields
             joinfield = self._interface.inputs.copyable_trait_names()
-        elif isinstance(joinfield, str):
+        elif isinstance(joinfield, six.string_types):
             joinfield = [joinfield]
         self.joinfield = joinfield
         """the fields to join"""
@@ -2047,7 +2048,7 @@ def __init__(self, interface, iterfield, name, serial=False, **kwargs):
 
 
         super(MapNode, self).__init__(interface, name, **kwargs)
-        if isinstance(iterfield, str):
+        if isinstance(iterfield, six.string_types):
             iterfield = [iterfield]
         self.iterfield = iterfield
         self._inputs = self._create_dynamic_traits(self._interface.inputs,
diff --git a/nipype/pipeline/utils.py b/nipype/pipeline/utils.py
index 21f7ef4036..b1889f0577 100644
--- a/nipype/pipeline/utils.py
+++ b/nipype/pipeline/utils.py
@@ -13,6 +13,7 @@
 
 import numpy as np
 from nipype.utils.misc import package_check
+from nipype.external import six
 
 package_check('networkx', '1.3')
 from socket import gethostname
@@ -103,7 +104,7 @@ def modify_paths(object, relative=True, basedir=None):
             out = tuple(out)
     else:
         if isdefined(object):
-            if isinstance(object, str) and os.path.isfile(object):
+            if isinstance(object, six.string_types) and os.path.isfile(object):
                 if relative:
                     if config.getboolean('execution', 'use_relative_paths'):
                         out = relpath(object, start=basedir)
@@ -186,7 +187,7 @@ def _write_detailed_dot(graph, dotfilename):
         inports = []
         for u, v, d in graph.in_edges_iter(nbunch=n, data=True):
             for cd in d['connect']:
-                if isinstance(cd[0], str):
+                if isinstance(cd[0], six.string_types):
                     outport = cd[0]
                 else:
                     outport = cd[0][0]
@@ -206,7 +207,7 @@ def _write_detailed_dot(graph, dotfilename):
         outports = []
         for u, v, d in graph.out_edges_iter(nbunch=n, data=True):
             for cd in d['connect']:
-                if isinstance(cd[0], str):
+                if isinstance(cd[0], six.string_types):
                     outport = cd[0]
                 else:
                     outport = cd[0][0]
@@ -607,7 +608,7 @@ def generate_expanded_graph(graph_in):
             # the itersource is a (node name, fields) tuple
             src_name, src_fields = inode.itersource
             # convert a single field to a list
-            if isinstance(src_fields, str):
+            if isinstance(src_fields, six.string_types):
                 src_fields = [src_fields]
             # find the unique iterable source node in the graph
             try:
@@ -789,7 +790,7 @@ def _standardize_iterables(node):
     if node.synchronize:
         if len(iterables) == 2:
             first, last = iterables
-            if all((isinstance(item, str) and item in fields
+            if all((isinstance(item, six.string_types) and item in fields
                     for item in first)):
                 iterables = _transpose_iterables(first, last)
 
@@ -961,7 +962,7 @@ def walk_outputs(object):
             if isdefined(val):
                 out.extend(walk_outputs(val))
     else:
-        if isdefined(object) and isinstance(object, basestring):
+        if isdefined(object) and isinstance(object, six.string_types):
             if os.path.islink(object) or os.path.isfile(object):
                 out = [(filename, 'f') for filename in get_all_files(object)]
             elif os.path.isdir(object):
diff --git a/nipype/testing/decorators.py b/nipype/testing/decorators.py
index a2e7e581c3..2591b76ea1 100644
--- a/nipype/testing/decorators.py
+++ b/nipype/testing/decorators.py
@@ -5,6 +5,7 @@
 """
 
 from numpy.testing.decorators import *
+from nipype.external import six
 
 from nibabel.data import DataError
 
@@ -44,7 +45,7 @@ def make_label_dec(label, ds=None):
     >>> f.hard
     True
     """
-    if isinstance(label,basestring):
+    if isinstance(label,six.string_types):
         labels = [label]
     else:
         labels = label
diff --git a/nipype/utils/docparse.py b/nipype/utils/docparse.py
index a380a8932d..2a60d257e1 100644
--- a/nipype/utils/docparse.py
+++ b/nipype/utils/docparse.py
@@ -16,6 +16,7 @@
 import subprocess
 from nipype.interfaces.base import CommandLine
 from nipype.utils.misc import is_container
+from nipype.external import six
 
 def grab_doc(cmd, trap_error=True):
     """Run cmd without args and grab documentation.
@@ -277,7 +278,7 @@ def _parse_doc(doc, style=['--']):
     # individual flag/option.
     doclist = doc.split('\n')
     optmap = {}
-    if isinstance(style,str):
+    if isinstance(style,six.string_types):
         style = [style]
     for line in doclist:
         linelist = line.split()
diff --git a/nipype/utils/provenance.py b/nipype/utils/provenance.py
index a51173ba9c..10fb20552f 100644
--- a/nipype/utils/provenance.py
+++ b/nipype/utils/provenance.py
@@ -4,6 +4,7 @@
 import pwd
 from socket import getfqdn
 from uuid import uuid1
+from nipype.external import six
 
 import numpy as np
 try:
@@ -94,7 +95,7 @@ def _get_sorteddict(object, dictwithhash=False):
         if isinstance(object, tuple):
             out = tuple(out)
     else:
-        if isinstance(object, str) and os.path.isfile(object):
+        if isinstance(object, six.string_types) and os.path.isfile(object):
             hash = hash_infile(object)
             if dictwithhash:
                 out = (object, hash)
@@ -213,7 +214,7 @@ def prov_encode(graph, value, create_container=True):
     else:
         encoded_literal = safe_encode(value)
         attr = {pm.PROV['value']: encoded_literal}
-        if isinstance(value, basestring) and os.path.exists(value):
+        if isinstance(value, six.string_types) and os.path.exists(value):
             attr.update({pm.PROV['location']: encoded_literal})
             if not os.path.isdir(value):
                 sha512 = hash_infile(value, crypto=hashlib.sha512)
diff --git a/tools/checkspecs.py b/tools/checkspecs.py
index ec70f01a9e..6dd6b5133a 100644
--- a/tools/checkspecs.py
+++ b/tools/checkspecs.py
@@ -12,6 +12,7 @@
 import tempfile
 import warnings
 
+from nipype.external import six
 from nipype.interfaces.base import BaseInterface
 
 # Functions and classes
@@ -215,7 +216,7 @@ def test_specs(self, uri):
                         for key, value in sorted(trait.__dict__.items()):
                             if key in in_built or key == 'desc':
                                 continue
-                            if isinstance(value, basestring):
+                            if isinstance(value, six.string_types):
                                 quote = "'"
                                 if "'" in value:
                                     quote = '"'
@@ -257,7 +258,7 @@ def test_specs(self, uri):
                         for key, value in sorted(trait.__dict__.items()):
                             if key in in_built or key == 'desc':
                                 continue
-                            if isinstance(value, basestring):
+                            if isinstance(value, six.string_types):
                                 quote = "'"
                                 if "'" in value:
                                     quote = '"'