diff --git a/src/sage/sat/boolean_polynomials.py b/src/sage/sat/boolean_polynomials.py
index 9392b66709e..7f962053e8a 100644
--- a/src/sage/sat/boolean_polynomials.py
+++ b/src/sage/sat/boolean_polynomials.py
@@ -25,6 +25,9 @@
 from sage.rings.polynomial.multi_polynomial_sequence import PolynomialSequence
 
 
+import six
+
+
 def solve(F, converter=None, solver=None, n=1, target_variables=None, **kwds):
     """
     Solve system of Boolean polynomials ``F`` by solving the
@@ -157,7 +160,7 @@ def solve(F, converter=None, solver=None, n=1, target_variables=None, **kwds):
 
     if not isinstance(solver, SatSolver):
         solver_kwds = {}
-        for k, v in kwds.iteritems():
+        for k, v in six.iteritems(kwds):
             if k.startswith("s_"):
                 solver_kwds[k[2:]] = v
 
@@ -170,7 +173,7 @@ def solve(F, converter=None, solver=None, n=1, target_variables=None, **kwds):
 
     if not isinstance(converter, ANF2CNFConverter):
         converter_kwds = {}
-        for k, v in kwds.iteritems():
+        for k, v in six.iteritems(kwds):
             if k.startswith("c_"):
                 converter_kwds[k[2:]] = v
 
@@ -308,7 +311,7 @@ def learn(F, converter=None, solver=None, max_learnt_length=3, interreduction=Fa
         from sage.sat.solvers.cryptominisat import CryptoMiniSat as solver
 
     solver_kwds = {}
-    for k, v in kwds.iteritems():
+    for k, v in six.iteritems(kwds):
         if k.startswith("s_"):
             solver_kwds[k[2:]] = v
 
@@ -320,7 +323,7 @@ def learn(F, converter=None, solver=None, max_learnt_length=3, interreduction=Fa
         from sage.sat.converters.polybori import CNFEncoder as converter
 
     converter_kwds = {}
-    for k, v in kwds.iteritems():
+    for k, v in six.iteritems(kwds):
         if k.startswith("c_"):
             converter_kwds[k[2:]] = v
 
diff --git a/src/sage/sat/converters/polybori.py b/src/sage/sat/converters/polybori.py
index c890d9a26b0..49f6cf7d822 100644
--- a/src/sage/sat/converters/polybori.py
+++ b/src/sage/sat/converters/polybori.py
@@ -35,6 +35,9 @@
 from sage.combinat.permutation import Permutations
 from sage.sat.converters import ANF2CNFConverter
 
+import six
+
+
 class CNFEncoder(ANF2CNFConverter):
     """
     ANF to CNF Converter using a Dense/Sparse Strategy. This converter distinguishes two classes of
@@ -278,13 +281,13 @@ def clauses_sparse(self, f):
         # any zero block of f+1
 
         blocks = self.zero_blocks(f+1)
-        C = [dict([(variable, 1-value) for (variable, value) in b.iteritems()]) for b in blocks ]
+        C = [dict([(variable, 1-value) for (variable, value) in six.iteritems(b)]) for b in blocks ]
 
         def to_dimacs_index(v):
             return v.index()+1
 
         def clause(c):
-            return [to_dimacs_index(variable) if value == 1 else -to_dimacs_index(variable) for (variable, value) in c.iteritems()]
+            return [to_dimacs_index(variable) if value == 1 else -to_dimacs_index(variable) for (variable, value) in six.iteritems(c)]
 
         for c in C:
             self.solver.add_clause(clause(c))
diff --git a/src/sage/symbolic/units.py b/src/sage/symbolic/units.py
index edac658c4da..4da3af37de3 100644
--- a/src/sage/symbolic/units.py
+++ b/src/sage/symbolic/units.py
@@ -91,6 +91,7 @@
 
 # standard Python libraries
 import re
+import six
 
 # Sage library
 from .ring import SR
@@ -500,8 +501,8 @@ def evalunitdict():
         sage: sage.symbolic.units.evalunitdict()
     """
     from sage.misc.all import sage_eval
-    for key, value in unitdict.iteritems():
-        unitdict[key] = dict([(a,sage_eval(repr(b))) for a, b in value.iteritems()])
+    for key, value in six.iteritems(unitdict):
+        unitdict[key] = dict([(a,sage_eval(repr(b))) for a, b in six.iteritems(value)])
 
     # FEATURE IDEA: create a function that would allow users to add
     # new entries to the table without having to know anything about
@@ -510,7 +511,7 @@ def evalunitdict():
     #
     # Format the table for easier use.
     #
-    for k, v in unitdict.iteritems():
+    for k, v in six.iteritems(unitdict):
         for a in v: unit_to_type[a] = k
 
     for w in unitdict:
diff --git a/src/sage/tensor/differential_form_element.py b/src/sage/tensor/differential_form_element.py
index b4a1b274cbc..69669940f27 100644
--- a/src/sage/tensor/differential_form_element.py
+++ b/src/sage/tensor/differential_form_element.py
@@ -30,6 +30,9 @@
 from sage.combinat.permutation import Permutation
 
 
+import six
+
+
 def sort_subscript(subscript):
     """
     A subscript is a range of integers.  This function sorts a subscript
@@ -569,8 +572,8 @@ def __eq__(self, other):
                 # pairs as we go along.
 
                 for (key1, val1), (key2, val2) in \
-                        zip(self._components.iteritems(), \
-                            other._components.iteritems()):
+                        zip(six.iteritems(self._components), \
+                            six.iteritems(other._components)):
                     if key1 != key2 or str(val1) != str(val2):
                         return False
                 return True
diff --git a/src/sage/tensor/modules/ext_pow_free_module.py b/src/sage/tensor/modules/ext_pow_free_module.py
index 9c0f044c3f3..4bce4698724 100644
--- a/src/sage/tensor/modules/ext_pow_free_module.py
+++ b/src/sage/tensor/modules/ext_pow_free_module.py
@@ -44,6 +44,9 @@
 from sage.tensor.modules.free_module_tensor import FreeModuleTensor
 from sage.tensor.modules.free_module_alt_form import FreeModuleAltForm
 
+import six
+
+
 class ExtPowerFreeModule(FiniteRankFreeModule):
     r"""
     Class for the exterior powers of the dual of a free module of finite rank
@@ -320,7 +323,7 @@ def _element_constructor_(self, comp=[], basis=None, name=None,
                                          tensor.base_module() is self._fmodule:
                 resu = self.element_class(self._fmodule, 1, name=tensor._name,
                                           latex_name=tensor._latex_name)
-                for basis, comp in tensor._components.iteritems():
+                for basis, comp in six.iteritems(tensor._components):
                     resu._components[basis] = comp.copy()
                 return resu
             else:
diff --git a/src/sage/tensor/modules/free_module_alt_form.py b/src/sage/tensor/modules/free_module_alt_form.py
index e9630fb102f..a8630788b0e 100644
--- a/src/sage/tensor/modules/free_module_alt_form.py
+++ b/src/sage/tensor/modules/free_module_alt_form.py
@@ -43,6 +43,9 @@
 from sage.tensor.modules.free_module_tensor import FreeModuleTensor
 from sage.tensor.modules.comp import Components, CompFullyAntiSym
 
+import six
+
+
 class FreeModuleAltForm(FreeModuleTensor):
     r"""
     Alternating form on a free module of finite rank over a commutative ring.
@@ -636,8 +639,8 @@ def wedge(self, other):
         cmp_r = CompFullyAntiSym(fmodule._ring, basis, rank_r,
                                  start_index=fmodule._sindex,
                                  output_formatter=fmodule._output_formatter)
-        for ind_s, val_s in cmp_s._comp.iteritems():
-            for ind_o, val_o in cmp_o._comp.iteritems():
+        for ind_s, val_s in six.iteritems(cmp_s._comp):
+            for ind_o, val_o in six.iteritems(cmp_o._comp):
                 ind_r = ind_s + ind_o
                 if len(ind_r) == len(set(ind_r)): # all indices are different
                     cmp_r[[ind_r]] += val_s * val_o
diff --git a/src/sage/tensor/modules/free_module_linear_group.py b/src/sage/tensor/modules/free_module_linear_group.py
index b4ebc96348d..f71e0c421f5 100644
--- a/src/sage/tensor/modules/free_module_linear_group.py
+++ b/src/sage/tensor/modules/free_module_linear_group.py
@@ -35,6 +35,9 @@
 from sage.tensor.modules.finite_rank_free_module import FiniteRankFreeModule
 from sage.tensor.modules.free_module_automorphism import FreeModuleAutomorphism
 
+import six
+
+
 class FreeModuleLinearGroup(UniqueRepresentation, Parent):
     r"""
     General linear group of a free module of finite rank over a commutative
@@ -371,7 +374,7 @@ def _element_constructor_(self, comp=[], basis=None, name=None,
             if tens.tensor_type() == (1,1):
                 resu = self.element_class(self._fmodule, name=tens._name,
                                           latex_name=tens._latex_name)
-                for basis, comp in tens._components.iteritems():
+                for basis, comp in six.iteritems(tens._components):
                     resu._components[basis] = comp.copy()
                 # Check whether the tensor is invertible:
                 try:
@@ -388,7 +391,7 @@ def _element_constructor_(self, comp=[], basis=None, name=None,
             if endo.is_endomorphism() and self._fmodule is endo.domain():
                 resu = self.element_class(self._fmodule, name=endo._name,
                                           latex_name=endo._latex_name)
-                for basis, mat in endo._matrices.iteritems():
+                for basis, mat in six.iteritems(endo._matrices):
                     resu.add_comp(basis[0])[:] = mat
                 # Check whether the endomorphism is invertible:
                 try:
diff --git a/src/sage/tensor/modules/free_module_morphism.py b/src/sage/tensor/modules/free_module_morphism.py
index 7f393430a35..0ba6fb25cd8 100644
--- a/src/sage/tensor/modules/free_module_morphism.py
+++ b/src/sage/tensor/modules/free_module_morphism.py
@@ -31,6 +31,9 @@
 from sage.categories.homset import Hom
 from sage.tensor.modules.finite_rank_free_module import FiniteRankFreeModule
 
+import six
+
+
 class FiniteRankFreeModuleMorphism(Morphism):
     r"""
     Homomorphism between free modules of finite rank over a commutative ring.
@@ -714,7 +717,7 @@ def _lmul_(self, scalar):
             True
         """
         resu = self.__class__(self.parent(), 0)  # 0 = provisory value
-        for bases, mat in self._matrices.iteritems():
+        for bases, mat in six.iteritems(self._matrices):
             resu._matrices[bases] = scalar * mat
         return resu
 
@@ -752,7 +755,7 @@ def __pos__(self):
         """
         resu = self.__class__(self.parent(), 0, is_identity=self._is_identity)
                                            # 0 = provisory value
-        for bases, mat in self._matrices.iteritems():
+        for bases, mat in six.iteritems(self._matrices):
             resu._matrices[bases] = +mat
         if self._name is not None:
             resu._name = '+' + self._name
@@ -789,7 +792,7 @@ def __neg__(self):
 
         """
         resu = self.__class__(self.parent(), 0)  # 0 = provisory value
-        for bases, mat in self._matrices.iteritems():
+        for bases, mat in six.iteritems(self._matrices):
             resu._matrices[bases] = -mat
         if self._name is not None:
             resu._name = '-' + self._name
diff --git a/src/sage/tensor/modules/free_module_tensor.py b/src/sage/tensor/modules/free_module_tensor.py
index 4842093f9df..c760bada0f5 100644
--- a/src/sage/tensor/modules/free_module_tensor.py
+++ b/src/sage/tensor/modules/free_module_tensor.py
@@ -193,6 +193,9 @@ class :class:`~sage.tensor.modules.tensor_free_module.TensorFreeModule`.
                                       CompFullyAntiSym)
 from sage.tensor.modules.tensor_with_indices import TensorWithIndices
 
+import six
+
+
 class FreeModuleTensor(ModuleElement):
     r"""
     Tensor over a free module of finite rank over a commutative ring.
@@ -1431,7 +1434,7 @@ def copy(self):
 
         """
         resu = self._new_instance()
-        for basis, comp in self._components.iteritems():
+        for basis, comp in six.iteritems(self._components):
              resu._components[basis] = comp.copy()
         return resu
 
diff --git a/src/sage/tensor/modules/tensor_free_module.py b/src/sage/tensor/modules/tensor_free_module.py
index 08351163b56..cfc713f3759 100644
--- a/src/sage/tensor/modules/tensor_free_module.py
+++ b/src/sage/tensor/modules/tensor_free_module.py
@@ -68,6 +68,9 @@
                                                    FiniteRankFreeModuleMorphism
 from sage.tensor.modules.free_module_automorphism import FreeModuleAutomorphism
 
+import six
+
+
 class TensorFreeModule(FiniteRankFreeModule):
     r"""
     Class for the free modules over a commutative ring `R` that are
@@ -447,7 +450,7 @@ def _element_constructor_(self, comp=[], basis=None, name=None,
                 resu = self.element_class(self._fmodule, (1,1),
                                           name=endo._name,
                                           latex_name=endo._latex_name)
-                for basis, mat in endo._matrices.iteritems():
+                for basis, mat in six.iteritems(endo._matrices):
                     resu.add_comp(basis[0])[:] = mat
             else:
                 raise TypeError("cannot coerce the {}".format(endo) +
@@ -467,7 +470,7 @@ def _element_constructor_(self, comp=[], basis=None, name=None,
             resu = self.element_class(self._fmodule, (0,p), name=form._name,
                                       latex_name=form._latex_name,
                                       antisym=asym)
-            for basis, comp in form._components.iteritems():
+            for basis, comp in six.iteritems(form._components):
                 resu._components[basis] = comp.copy()
         elif isinstance(comp, FreeModuleAutomorphism):
             # coercion of an automorphism to a type-(1,1) tensor:
@@ -478,7 +481,7 @@ def _element_constructor_(self, comp=[], basis=None, name=None,
                                 " to an element of {}".format(self))
             resu = self.element_class(self._fmodule, (1,1), name=autom._name,
                                       latex_name=autom._latex_name)
-            for basis, comp in autom._components.iteritems():
+            for basis, comp in six.iteritems(autom._components):
                 resu._components[basis] = comp.copy()
         else:
             # Standard construction:
diff --git a/src/sage_setup/docbuild/ext/inventory_builder.py b/src/sage_setup/docbuild/ext/inventory_builder.py
index 5a98ad8649e..78d0ea4f23a 100644
--- a/src/sage_setup/docbuild/ext/inventory_builder.py
+++ b/src/sage_setup/docbuild/ext/inventory_builder.py
@@ -9,6 +9,10 @@
 from sphinx.builders.html import StandaloneHTMLBuilder
 from sphinx.util.console import bold
 from os import path
+
+import six
+
+
 try:
     from hashlib import md5
 except ImportError:
@@ -24,7 +28,7 @@ class InventoryBuilder(StandaloneHTMLBuilder):
 
     def get_outdated_docs(self):
         cfgdict = dict((name, self.config[name])
-                       for (name, desc) in self.config.values.iteritems()
+                       for (name, desc) in six.iteritems(self.config.values)
                        if desc[1] == 'html')
         self.config_hash = md5(unicode(cfgdict).encode('utf-8')).hexdigest()
         self.tags_hash = md5(unicode(sorted(self.tags)).encode('utf-8')) \
diff --git a/src/sage_setup/docbuild/ext/multidocs.py b/src/sage_setup/docbuild/ext/multidocs.py
index a0474ada5db..63dbb712616 100644
--- a/src/sage_setup/docbuild/ext/multidocs.py
+++ b/src/sage_setup/docbuild/ext/multidocs.py
@@ -20,6 +20,7 @@
     - the javascript index;
     - the citations.
 """
+import six
 from six.moves import cPickle
 import os
 import sys
@@ -87,14 +88,14 @@ def merge_environment(app, env):
                 env.metadata[ind] = md
             # merge the citations
             newcite = {}
-            for ind, (path, tag) in docenv.citations.iteritems():
+            for ind, (path, tag) in six.iteritems(docenv.citations):
                 # TODO: Warn on conflicts
                 newcite[ind] = (fixpath(path), tag)
             env.citations.update(newcite)
             # merge the py:module indexes
             newmodules = {}
             for ind,(modpath,v1,v2,v3) in (
-                docenv.domaindata['py']['modules'].iteritems()):
+                six.iteritems(docenv.domaindata['py']['modules'])):
                 newmodules[ind] = (fixpath(modpath),v1,v2,v3)
             env.domaindata['py']['modules'].update(newmodules)
             app.info(", %s modules"%(len(newmodules)))
@@ -136,14 +137,14 @@ def merge_js_index(app):
         if index is not None:
             # merge the mappings
             app.info(" %s js index entries"%(len(index._mapping)))
-            for (ref, locs) in index._mapping.iteritems():
+            for (ref, locs) in six.iteritems(index._mapping):
                 newmapping = set(map(fixpath, locs))
                 if ref in mapping:
                     newmapping = mapping[ref] | newmapping
                 mapping[unicode(ref)] = newmapping
             # merge the titles
             titles = app.builder.indexer._titles
-            for (res, title) in index._titles.iteritems():
+            for (res, title) in six.iteritems(index._titles):
                 titles[fixpath(res)] = title
             # TODO: merge indexer._objtypes, indexer._objnames as well
 
@@ -244,7 +245,7 @@ def fetch_citation(app, env):
         cache = cPickle.load(f)
     app.builder.info("done (%s citations)."%len(cache))
     cite = env.citations
-    for ind, (path, tag) in cache.iteritems():
+    for ind, (path, tag) in six.iteritems(cache):
         if ind not in cite: # don't override local citation
             cite[ind]=(os.path.join("..", path), tag)