diff --git a/.travis.yml b/.travis.yml
index f5db6cac09e05c..287c6337cbda4d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -87,7 +87,7 @@ matrix:
         apt:
           packages:
             - libnss3-tools
-      env: JOB=wpt_integration TOXENV=py27 SCRIPT=tools/ci/ci_wpt.sh
+      env: JOB=wpt_integration TOXENV=py27,py27-flake8 SCRIPT=tools/ci/ci_wpt.sh
   exclude:
     - env:  # exclude empty env from the top-level above
   allow_failures:
diff --git a/tools/ci/check_stability.py b/tools/ci/check_stability.py
index 169962a55e6f2c..322a52140a205b 100644
--- a/tools/ci/check_stability.py
+++ b/tools/ci/check_stability.py
@@ -132,11 +132,6 @@ def get_sha1():
     return git("rev-parse", "HEAD").strip()
 
 
-def install_wptrunner():
-    """Install wptrunner."""
-    call("pip", "install", wptrunner_root)
-
-
 def deepen_checkout(user):
     """Convert from a shallow checkout to a full one"""
     fetch_args = [user, "+refs/heads/*:refs/remotes/origin/*"]
diff --git a/tools/ci/ci_tools_unittest.sh b/tools/ci/ci_tools_unittest.sh
index 6c74a2512441dc..7a54d85ff0aa50 100755
--- a/tools/ci/ci_tools_unittest.sh
+++ b/tools/ci/ci_tools_unittest.sh
@@ -16,6 +16,7 @@ fi
 
 if [[ $(./wpt test-jobs --includes wptrunner_unittest; echo $?) -eq 0 ]]; then
     if [ $TOXENV == "py27" ] || [ $TOXENV == "pypy" ]; then
+        TOXENV="$TOXENV,py27-flake8"
         cd tools/wptrunner
         tox
     fi
diff --git a/tools/manifest/XMLParser.py b/tools/manifest/XMLParser.py
index 5ceeb0b5f72719..523f544b7c4e83 100644
--- a/tools/manifest/XMLParser.py
+++ b/tools/manifest/XMLParser.py
@@ -70,8 +70,8 @@ def _data(self, text):
     def _end(self, tag):
         return self._target.end(_fixname(tag))
 
-    def _external(self, context, base, systemId, publicId):
-        if publicId in {
+    def _external(self, context, base, system_id, public_id):
+        if public_id in {
                 "-//W3C//DTD XHTML 1.0 Transitional//EN",
                 "-//W3C//DTD XHTML 1.1//EN",
                 "-//W3C//DTD XHTML 1.0 Strict//EN",
diff --git a/tools/manifest/manifest.py b/tools/manifest/manifest.py
index b153798d6f96b0..e466e6ff56ae3b 100644
--- a/tools/manifest/manifest.py
+++ b/tools/manifest/manifest.py
@@ -2,7 +2,7 @@
 import os
 import re
 from collections import defaultdict
-from six import iteritems, itervalues, viewkeys
+from six import iteritems, itervalues, viewkeys, string_types
 
 from .item import ManualTest, WebdriverSpecTest, Stub, RefTestNode, RefTest, TestharnessTest, SupportFile, ConformanceCheckerTest, VisualTest
 from .log import get_logger
@@ -20,14 +20,6 @@ class ManifestVersionMismatch(ManifestError):
     pass
 
 
-def sourcefile_items(args):
-    tests_root, url_base, rel_path, status = args
-    source_file = SourceFile(tests_root,
-                             rel_path,
-                             url_base)
-    return rel_path, source_file.manifest_items()
-
-
 class Manifest(object):
     def __init__(self, url_base="/"):
         assert url_base is not None
@@ -221,7 +213,7 @@ def load(tests_root, manifest):
     logger = get_logger()
 
     # "manifest" is a path or file-like object.
-    if isinstance(manifest, basestring):
+    if isinstance(manifest, string_types):
         if os.path.exists(manifest):
             logger.debug("Opening manifest at %s" % manifest)
         else:
diff --git a/tools/runner/report.py b/tools/runner/report.py
index f4b3fa71661a74..952df08b805989 100644
--- a/tools/runner/report.py
+++ b/tools/runner/report.py
@@ -1,3 +1,5 @@
+# flake8: noqa
+
 from __future__ import print_function
 
 import argparse
diff --git a/tools/sslutils/base.py b/tools/sslutils/base.py
index e78e1385c7be08..237ae5f23ccf1f 100644
--- a/tools/sslutils/base.py
+++ b/tools/sslutils/base.py
@@ -1,9 +1,3 @@
-def get_logger(name="ssl"):
-    logger = structured.get_default_logger(name)
-    if logger is None:
-        logger = structured.structuredlog.StructuredLogger(name)
-    return logger
-
 class NoSSLEnvironment(object):
     ssl_enabled = False
 
diff --git a/tools/tox.ini b/tools/tox.ini
index b154c471d6f18d..159a934eb1a6ba 100644
--- a/tools/tox.ini
+++ b/tools/tox.ini
@@ -3,8 +3,12 @@ envlist = py27,py36,pypy
 skipsdist=True
 
 [testenv]
+# flake8 versions should be kept in sync across tools/tox.ini, tools/wpt/tox.ini, and tools/wptrunner/tox.ini
 deps =
-  flake8
+  flake8==3.5.0
+  pycodestyle==2.3.1
+  pyflakes==1.6.0
+  pep8-naming==0.4.1
   pytest
   pytest-cov
   mock
@@ -19,6 +23,28 @@ passenv =
   HYPOTHESIS_PROFILE
 
 [flake8]
-ignore = E128,E129,E221,E226,E231,E251,E265,E302,E303,E305,E402,E901,F401,F821,F841
+# flake8 config should be kept in sync across tools/tox.ini, tools/wpt/tox.ini, and tools/wptrunner/tox.ini
+select = E,W,F,N
+# E128: continuation line under-indented for visual indent
+# E129: visually indented line with same indent as next logical line
+# E221: multiple spaces before operator
+# E226: missing whitespace around arithmetic operator
+# E231: missing whitespace after ‘,’, ‘;’, or ‘:’
+# E251: unexpected spaces around keyword / parameter equals
+# E265: block comment should start with ‘# ‘
+# E302: expected 2 blank lines, found 0
+# E303: too many blank lines (3)
+# E305: expected 2 blank lines after end of function or class
+# E402: module level import not at top of file
+# E731: do not assign a lambda expression, use a def
+# E901: SyntaxError or IndentationError
+# W601: .has_key() is deprecated, use ‘in’
+# F401: module imported but unused
+# F403: ‘from module import *’ used; unable to detect undefined names
+# F405: name may be undefined, or defined from star imports: module
+# F841: local variable name is assigned to but never used
+# N801: class names should use CapWords convention
+# N802: function name should be lowercase
+ignore = E128,E129,E221,E226,E231,E251,E265,E302,E303,E305,E402,E731,E901,W601,F401,F403,F405,F841,N801,N802
 max-line-length = 141
 exclude = .tox,html5lib,third_party/py,third_party/pytest,third_party/funcsigs,third_party/attrs,third_party/pluggy/,pywebsocket,six,_venv,webencodings,wptserve/docs,wptserve/tests/functional/docroot/,wpt,wptrunner
diff --git a/tools/webdriver/webdriver/client.py b/tools/webdriver/webdriver/client.py
index ec7d6deccbacf0..622c5fce76acc2 100644
--- a/tools/webdriver/webdriver/client.py
+++ b/tools/webdriver/webdriver/client.py
@@ -4,6 +4,8 @@
 import protocol
 import transport
 
+from six import string_types
+
 from mozlog import get_default_logger
 
 logger = get_default_logger()
@@ -313,7 +315,7 @@ def __setitem__(self, name, value):
         cookie = {"name": name,
                   "value": None}
 
-        if isinstance(name, (str, unicode)):
+        if isinstance(name, string_types):
             cookie["value"] = value
         elif hasattr(value, "value"):
             cookie["value"] = value.value
diff --git a/tools/webdriver/webdriver/protocol.py b/tools/webdriver/webdriver/protocol.py
index 80f358c8b0ad8d..ea0c793accbda6 100644
--- a/tools/webdriver/webdriver/protocol.py
+++ b/tools/webdriver/webdriver/protocol.py
@@ -16,7 +16,7 @@ def default(self, obj):
             return [self.default(x) for x in obj]
         elif isinstance(obj, webdriver.Element):
             return {webdriver.Element.identifier: obj.id}
-        return super(ProtocolEncoder, self).default(obj)
+        return super(Encoder, self).default(obj)
 
 
 class Decoder(json.JSONDecoder):
diff --git a/tools/webdriver/webdriver/servo.py b/tools/webdriver/webdriver/servo.py
deleted file mode 100644
index 2e0b722ababe41..00000000000000
--- a/tools/webdriver/webdriver/servo.py
+++ /dev/null
@@ -1,18 +0,0 @@
-class ServoExtensionCommands(object):
-    def __init__(self, session):
-        self.session = session
-
-    @command
-    def get_prefs(self, *prefs):
-        body = {"prefs": list(prefs)}
-        return self.session.send_command("POST", "servo/prefs/get", body)
-
-    @command
-    def set_prefs(self, prefs):
-        body = {"prefs": prefs}
-        return self.session.send_command("POST", "servo/prefs/set", body)
-
-    @command
-    def reset_prefs(self, *prefs):
-        body = {"prefs": list(prefs)}
-        return self.session.send_command("POST", "servo/prefs/reset", body)
diff --git a/tools/webdriver/webdriver/transport.py b/tools/webdriver/webdriver/transport.py
index b198b194b38b23..d62271fe957caa 100644
--- a/tools/webdriver/webdriver/transport.py
+++ b/tools/webdriver/webdriver/transport.py
@@ -4,6 +4,7 @@
 
 import error
 
+from six import text_type
 
 """Implements HTTP transport for the WebDriver wire protocol."""
 
@@ -135,7 +136,7 @@ def send(self,
         except ValueError:
             raise ValueError("Failed to encode request body as JSON:\n"
                 "%s" % json.dumps(body, indent=2))
-        if isinstance(payload, unicode):
+        if isinstance(payload, text_type):
             payload = body.encode("utf-8")
 
         if headers is None:
diff --git a/tools/wpt/browser.py b/tools/wpt/browser.py
index 44cad5f04b212b..c6cc38afd67c00 100644
--- a/tools/wpt/browser.py
+++ b/tools/wpt/browser.py
@@ -4,9 +4,12 @@
 import re
 import shutil
 import stat
+import subprocess
+import sys
 from abc import ABCMeta, abstractmethod
 from ConfigParser import RawConfigParser
 from distutils.spawn import find_executable
+from io import BytesIO
 
 from utils import call, get, untar, unzip
 
diff --git a/tools/wpt/install.py b/tools/wpt/install.py
index 408744a4a405c2..d779651c990e2b 100644
--- a/tools/wpt/install.py
+++ b/tools/wpt/install.py
@@ -39,8 +39,3 @@ def install(name, component, destination):
     subclass = getattr(browser, name.title())
     sys.stdout.write('Now installing %s %s...\n' % (name, component))
     getattr(subclass(), method)(dest=destination)
-
-
-if __name__ == '__main__':
-    args = parser.parse_args()
-    run(None, **vars(args))
diff --git a/tools/wpt/markdown.py b/tools/wpt/markdown.py
index 87018910ac1f69..494dc2a3081fba 100644
--- a/tools/wpt/markdown.py
+++ b/tools/wpt/markdown.py
@@ -1,3 +1,5 @@
+from .stability import is_inconsistent
+
 def format_comment_title(product):
     """Produce a Markdown-formatted string based on a given "product"--a string
     containing a browser identifier optionally followed by a colon and a
diff --git a/tools/wpt/tox.ini b/tools/wpt/tox.ini
index 5836a52ffa9dcd..02c8f6a51cefea 100644
--- a/tools/wpt/tox.ini
+++ b/tools/wpt/tox.ini
@@ -1,10 +1,9 @@
 [tox]
-envlist = py27
+envlist = py27,py27-flake8
 skipsdist=True
 
 [testenv]
 deps =
-  flake8
   pytest
   pytest-cov
   hypothesis
@@ -14,8 +13,40 @@ deps =
 
 commands =
   pytest --cov
-  flake8
+
+[testenv:py27-flake8]
+# flake8 versions should be kept in sync across tools/tox.ini, tools/wpt/tox.ini, and tools/wptrunner/tox.ini
+deps =
+     flake8==3.5.0
+     pycodestyle==2.3.1
+     pyflakes==1.6.0
+     pep8-naming==0.4.1
+
+commands =
+     flake8
 
 [flake8]
-ignore = E128,E129,E221,E226,E231,E251,E265,E302,E303,E305,E402,E901,F401,F821,F841
+# flake8 config should be kept in sync across tools/tox.ini, tools/wpt/tox.ini, and tools/wptrunner/tox.ini
+select = E,W,F,N
+# E128: continuation line under-indented for visual indent
+# E129: visually indented line with same indent as next logical line
+# E221: multiple spaces before operator
+# E226: missing whitespace around arithmetic operator
+# E231: missing whitespace after ‘,’, ‘;’, or ‘:’
+# E251: unexpected spaces around keyword / parameter equals
+# E265: block comment should start with ‘# ‘
+# E302: expected 2 blank lines, found 0
+# E303: too many blank lines (3)
+# E305: expected 2 blank lines after end of function or class
+# E402: module level import not at top of file
+# E731: do not assign a lambda expression, use a def
+# E901: SyntaxError or IndentationError
+# W601: .has_key() is deprecated, use ‘in’
+# F401: module imported but unused
+# F403: ‘from module import *’ used; unable to detect undefined names
+# F405: name may be undefined, or defined from star imports: module
+# F841: local variable name is assigned to but never used
+# N801: class names should use CapWords convention
+# N802: function name should be lowercase
+ignore = E128,E129,E221,E226,E231,E251,E265,E302,E303,E305,E402,E731,E901,W601,F401,F403,F405,F841,N801,N802
 max-line-length = 141
diff --git a/tools/wpt/utils.py b/tools/wpt/utils.py
index e1f4cd4bb5c75d..e8edc0be493731 100644
--- a/tools/wpt/utils.py
+++ b/tools/wpt/utils.py
@@ -27,7 +27,7 @@ def set_if_none(self,
                 value = value()
             if not value:
                 if err_fn is not None:
-                    return err_fn(kwargs, "Failed to find %s" % desc)
+                    return err_fn(self, "Failed to find %s" % desc)
                 else:
                     return
             self[name] = value
diff --git a/tools/wpt/virtualenv.py b/tools/wpt/virtualenv.py
index e15f129176c1c4..b8454c979c2c4b 100644
--- a/tools/wpt/virtualenv.py
+++ b/tools/wpt/virtualenv.py
@@ -1,4 +1,5 @@
 import os
+import shutil
 import sys
 import logging
 from distutils.spawn import find_executable
diff --git a/tools/wptrunner/docs/conf.py b/tools/wptrunner/docs/conf.py
index 0c717f56536b9d..b58f313e946aa9 100644
--- a/tools/wptrunner/docs/conf.py
+++ b/tools/wptrunner/docs/conf.py
@@ -186,22 +186,22 @@
 # -- Options for LaTeX output ---------------------------------------------
 
 latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
+    # The paper size ('letterpaper' or 'a4paper').
+    #'papersize': 'letterpaper',
 
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
+    # The font size ('10pt', '11pt' or '12pt').
+    #'pointsize': '10pt',
 
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
+    # Additional stuff for the LaTeX preamble.
+    #'preamble': '',
 }
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
 latex_documents = [
-  ('index', 'wptrunner.tex', u'wptrunner Documentation',
-   u'James Graham', 'manual'),
+    ('index', 'wptrunner.tex', u'wptrunner Documentation',
+     u'James Graham', 'manual'),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
@@ -244,9 +244,9 @@
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
 texinfo_documents = [
-  ('index', 'wptrunner', u'wptrunner Documentation',
-   u'James Graham', 'wptrunner', 'One line description of project.',
-   'Miscellaneous'),
+    ('index', 'wptrunner', u'wptrunner Documentation',
+     u'James Graham', 'wptrunner', 'One line description of project.',
+     'Miscellaneous'),
 ]
 
 # Documents to append as an appendix to all manuals.
diff --git a/tools/wptrunner/setup.py b/tools/wptrunner/setup.py
index 7ec189fefd9aee..dc3048e259775c 100644
--- a/tools/wptrunner/setup.py
+++ b/tools/wptrunner/setup.py
@@ -59,7 +59,7 @@
       include_package_data=True,
       data_files=[("requirements", requirements_files)],
       install_requires=deps
-     )
+      )
 
 if "install" in sys.argv:
     path = os.path.relpath(os.path.join(sys.prefix, "requirements"), os.curdir)
diff --git a/tools/wptrunner/test/test.py b/tools/wptrunner/test/test.py
index 034e317bd52f08..622934a42b0cc0 100644
--- a/tools/wptrunner/test/test.py
+++ b/tools/wptrunner/test/test.py
@@ -156,7 +156,8 @@ def main():
         run(config, args)
     except Exception:
         if args.pdb:
-            import pdb, traceback
+            import pdb
+            import traceback
             print traceback.format_exc()
             pdb.post_mortem()
         else:
diff --git a/tools/wptrunner/tox.ini b/tools/wptrunner/tox.ini
index 790970409f3602..6088c1460bbabc 100644
--- a/tools/wptrunner/tox.ini
+++ b/tools/wptrunner/tox.ini
@@ -2,7 +2,7 @@
 xfail_strict=true
 
 [tox]
-envlist = {py27,pypy}-{base,b2g,chrome,firefox,servo}
+envlist = {py27,pypy}-{base,b2g,chrome,firefox,servo},py27-flake8
 
 [testenv]
 deps =
@@ -15,3 +15,40 @@ deps =
      servo: -r{toxinidir}/requirements_servo.txt
 
 commands = pytest --cov
+
+[testenv:py27-flake8]
+# flake8 versions should be kept in sync across tools/tox.ini, tools/wpt/tox.ini, and tools/wptrunner/tox.ini
+deps =
+     flake8==3.5.0
+     pycodestyle==2.3.1
+     pyflakes==1.6.0
+     pep8-naming==0.4.1
+
+commands =
+     flake8
+
+[flake8]
+# flake8 config should be kept in sync across tools/tox.ini, tools/wpt/tox.ini, and tools/wptrunner/tox.ini
+select = E,W,F,N
+# E128: continuation line under-indented for visual indent
+# E129: visually indented line with same indent as next logical line
+# E221: multiple spaces before operator
+# E226: missing whitespace around arithmetic operator
+# E231: missing whitespace after ‘,’, ‘;’, or ‘:’
+# E251: unexpected spaces around keyword / parameter equals
+# E265: block comment should start with ‘# ‘
+# E302: expected 2 blank lines, found 0
+# E303: too many blank lines (3)
+# E305: expected 2 blank lines after end of function or class
+# E402: module level import not at top of file
+# E731: do not assign a lambda expression, use a def
+# E901: SyntaxError or IndentationError
+# W601: .has_key() is deprecated, use ‘in’
+# F401: module imported but unused
+# F403: ‘from module import *’ used; unable to detect undefined names
+# F405: name may be undefined, or defined from star imports: module
+# F841: local variable name is assigned to but never used
+# N801: class names should use CapWords convention
+# N802: function name should be lowercase
+ignore = E128,E129,E221,E226,E231,E251,E265,E302,E303,E305,E402,E731,E901,W601,F401,F403,F405,F841,N801,N802
+max-line-length = 141
diff --git a/tools/wptrunner/wptrunner/browsers/firefox.py b/tools/wptrunner/wptrunner/browsers/firefox.py
index b324bccd91e2a4..6d1f58d3791624 100644
--- a/tools/wptrunner/wptrunner/browsers/firefox.py
+++ b/tools/wptrunner/wptrunner/browsers/firefox.py
@@ -96,15 +96,15 @@ def executor_kwargs(test_type, server_config, cache_manager, run_info_data,
         executor_kwargs["reftest_internal"] = kwargs["reftest_internal"]
         executor_kwargs["reftest_screenshot"] = kwargs["reftest_screenshot"]
     if test_type == "wdspec":
-        fxOptions = {}
+        options = {}
         if kwargs["binary"]:
-            fxOptions["binary"] = kwargs["binary"]
+            options["binary"] = kwargs["binary"]
         if kwargs["binary_args"]:
-            fxOptions["args"] = kwargs["binary_args"]
-        fxOptions["prefs"] = {
+            options["args"] = kwargs["binary_args"]
+        options["prefs"] = {
             "network.dns.localDomains": ",".join(hostnames)
         }
-        capabilities["moz:firefoxOptions"] = fxOptions
+        capabilities["moz:firefoxOptions"] = options
     if kwargs["certutil_binary"] is None:
         capabilities["acceptInsecureCerts"] = True
     if capabilities:
@@ -364,7 +364,7 @@ def setup_ssl(self):
 
         env[env_var] = (os.path.pathsep.join([certutil_dir, env[env_var]])
                         if env_var in env else certutil_dir).encode(
-                                sys.getfilesystemencoding() or 'utf-8', 'replace')
+                            sys.getfilesystemencoding() or 'utf-8', 'replace')
 
         def certutil(*args):
             cmd = [self.certutil_binary] + list(args)
diff --git a/tools/wptrunner/wptrunner/browsers/ie.py b/tools/wptrunner/wptrunner/browsers/ie.py
index 553372f390e745..13f5827194de3b 100644
--- a/tools/wptrunner/wptrunner/browsers/ie.py
+++ b/tools/wptrunner/wptrunner/browsers/ie.py
@@ -28,10 +28,10 @@ def executor_kwargs(test_type, server_config, cache_manager, run_info_data,
                     **kwargs):
     from selenium.webdriver import DesiredCapabilities
 
-    ieOptions = {}
-    ieOptions["requireWindowFocus"] = True
+    options = {}
+    options["requireWindowFocus"] = True
     capabilities = {}
-    capabilities["se:ieOptions"] = ieOptions
+    capabilities["se:ieOptions"] = options
     executor_kwargs = base_executor_kwargs(test_type, server_config,
                                            cache_manager, **kwargs)
     executor_kwargs["close_after_done"] = True
@@ -51,7 +51,7 @@ class InternetExplorerBrowser(Browser):
 
     def __init__(self, logger, webdriver_binary, webdriver_args=None):
         Browser.__init__(self, logger)
-        self.server = InterentExplorerDriverServer(self.logger,
+        self.server = InternetExplorerDriverServer(self.logger,
                                                    binary=webdriver_binary,
                                                    args=webdriver_args)
         self.webdriver_host = "localhost"
diff --git a/tools/wptrunner/wptrunner/environment.py b/tools/wptrunner/wptrunner/environment.py
index 874595cbff3f03..711534180dc69c 100644
--- a/tools/wptrunner/wptrunner/environment.py
+++ b/tools/wptrunner/wptrunner/environment.py
@@ -61,7 +61,7 @@ def get_ssl_kwargs(**kwargs):
     elif kwargs["ssl_type"] == "pregenerated":
         args = {"host_key_path": kwargs["host_key_path"],
                 "host_cert_path": kwargs["host_cert_path"],
-                 "ca_cert_path": kwargs["ca_cert_path"]}
+                "ca_cert_path": kwargs["ca_cert_path"]}
     else:
         args = {}
     return args
diff --git a/tools/wptrunner/wptrunner/executors/base.py b/tools/wptrunner/wptrunner/executors/base.py
index d87e4ab9924f3a..7178b2e28c374a 100644
--- a/tools/wptrunner/wptrunner/executors/base.py
+++ b/tools/wptrunner/wptrunner/executors/base.py
@@ -13,7 +13,7 @@
 
 # Extra timeout to use after internal test timeout at which the harness
 # should force a timeout
-extra_timeout = 5 # seconds
+extra_timeout = 5  # seconds
 
 
 def executor_kwargs(test_type, server_config, cache_manager, **kwargs):
@@ -67,8 +67,8 @@ def __call__(self, test, result):
                                       (result_url, test.url))
         harness_result = test.result_cls(self.harness_codes[status], message)
         return (harness_result,
-                [test.subtest_result_cls(name, self.test_codes[status], message, stack)
-                 for name, status, message, stack in subtest_results])
+                [test.subtest_result_cls(st_name, self.test_codes[st_status], st_message, st_stack)
+                 for st_name, st_status, st_message, st_stack in subtest_results])
 
 
 testharness_result_converter = TestharnessResultConverter()
@@ -124,7 +124,7 @@ def __init__(self, browser, server_config, timeout_multiplier=1,
         self.debug_info = debug_info
         self.last_environment = {"protocol": "http",
                                  "prefs": {}}
-        self.protocol = None # This must be set in subclasses
+        self.protocol = None  # This must be set in subclasses
 
     @property
     def logger(self):
diff --git a/tools/wptrunner/wptrunner/executors/executormarionette.py b/tools/wptrunner/wptrunner/executors/executormarionette.py
index 2d0dc914d10566..30930c3c2f9259 100644
--- a/tools/wptrunner/wptrunner/executors/executormarionette.py
+++ b/tools/wptrunner/wptrunner/executors/executormarionette.py
@@ -304,7 +304,7 @@ def __init__(self, logger, func, protocol, url, timeout):
         self.result_flag = threading.Event()
 
     def run(self):
-        index = self.url.rfind("/storage/");
+        index = self.url.rfind("/storage/")
         if index != -1:
             # Clear storage
             self.protocol.clear_origin(self.url)
@@ -503,7 +503,7 @@ def screenshot(self, test, viewport_size, dpi):
         assert viewport_size is None
         assert dpi is None
 
-        timeout =  self.timeout_multiplier * test.timeout if self.debug_info is None else None
+        timeout = self.timeout_multiplier * test.timeout if self.debug_info is None else None
 
         test_url = self.test_url(test)
 
diff --git a/tools/wptrunner/wptrunner/executors/executorselenium.py b/tools/wptrunner/wptrunner/executors/executorselenium.py
index 2e84ab6fd65dd6..f905fac81e10ec 100644
--- a/tools/wptrunner/wptrunner/executors/executorselenium.py
+++ b/tools/wptrunner/wptrunner/executors/executorselenium.py
@@ -51,7 +51,7 @@ def setup(self, runner):
             self.webdriver = webdriver.Remote(command_executor=RemoteConnection(self.url.strip("/"),
                                                                                 resolve_ip=False),
                                               desired_capabilities=self.capabilities)
-        except:
+        except Exception:
             self.logger.warning(
                 "Connecting to Selenium failed:\n%s" % traceback.format_exc())
         else:
@@ -64,7 +64,7 @@ def setup(self, runner):
         else:
             try:
                 self.after_connect()
-            except:
+            except Exception:
                 print >> sys.stderr, traceback.format_exc()
                 self.logger.warning(
                     "Failed to connect to navigate initial page")
@@ -76,7 +76,7 @@ def teardown(self):
         self.logger.debug("Hanging up on Selenium session")
         try:
             self.webdriver.quit()
-        except:
+        except Exception:
             pass
         del self.webdriver
 
@@ -103,7 +103,7 @@ def load_runner(self, protocol):
     def wait(self):
         while True:
             try:
-                self.webdriver.execute_async_script("");
+                self.webdriver.execute_async_script("")
             except exceptions.TimeoutException:
                 pass
             except (socket.timeout, exceptions.NoSuchWindowException,
@@ -220,7 +220,7 @@ def do_testharness(self, webdriver, url, timeout):
             win_s = webdriver.execute_script("return window['%s'];" % self.window_id)
             win_obj = json.loads(win_s)
             test_window = win_obj["window-fcc6-11e5-b4f8-330a88ab9d7f"]
-        except:
+        except Exception:
             after = webdriver.window_handles
             if len(after) == 2:
                 test_window = next(iter(set(after) - set([parent])))
diff --git a/tools/wptrunner/wptrunner/executors/executorservo.py b/tools/wptrunner/wptrunner/executors/executorservo.py
index 33ff10df9287c5..ca8ec8a7eb5abf 100644
--- a/tools/wptrunner/wptrunner/executors/executorservo.py
+++ b/tools/wptrunner/wptrunner/executors/executorservo.py
@@ -28,7 +28,7 @@
 pytestrunner = None
 webdriver = None
 
-extra_timeout = 5 # seconds
+extra_timeout = 5  # seconds
 
 hosts_text = """127.0.0.1 web-platform.test
 127.0.0.1 www.web-platform.test
diff --git a/tools/wptrunner/wptrunner/executors/executorservodriver.py b/tools/wptrunner/wptrunner/executors/executorservodriver.py
index af09da6f1788db..ed7afaf1028b8b 100644
--- a/tools/wptrunner/wptrunner/executors/executorservodriver.py
+++ b/tools/wptrunner/wptrunner/executors/executorservodriver.py
@@ -43,7 +43,7 @@ def setup(self, runner):
             self.session = webdriver.Session(self.host, self.port,
                 extension=webdriver.servo.ServoCommandExtensions)
             self.session.start()
-        except:
+        except Exception:
             self.logger.warning(
                 "Connecting with WebDriver failed:\n%s" % traceback.format_exc())
         else:
@@ -60,7 +60,7 @@ def teardown(self):
         self.logger.debug("Hanging up on WebDriver session")
         try:
             self.session.end()
-        except:
+        except Exception:
             pass
 
     def is_alive(self):
diff --git a/tools/wptrunner/wptrunner/manifestupdate.py b/tools/wptrunner/wptrunner/manifestupdate.py
index fd3f82aeb113a9..1d3c173928f03f 100644
--- a/tools/wptrunner/wptrunner/manifestupdate.py
+++ b/tools/wptrunner/wptrunner/manifestupdate.py
@@ -247,8 +247,8 @@ def coalesce_expected(self, stability=None):
                         boolean_properties=self.root.boolean_properties)
                 except ConditionError as e:
                     if stability is not None:
-                       self.set("disabled", stability or "unstable", e.cond.children[0])
-                       self.new_disabled = True
+                        self.set("disabled", stability or "unstable", e.cond.children[0])
+                        self.new_disabled = True
                     else:
                         print "Conflicting test results for %s, cannot update" % self.root.test_path
                     return
diff --git a/tools/wptrunner/wptrunner/metadata.py b/tools/wptrunner/wptrunner/metadata.py
index 923ac7907335c4..9c31e4279ef660 100644
--- a/tools/wptrunner/wptrunner/metadata.py
+++ b/tools/wptrunner/wptrunner/metadata.py
@@ -355,7 +355,7 @@ def load_expected(test_manifest, metadata_path, test_path, tests, property_order
 
     # Remove expected data for tests that no longer exist
     for test in expected_manifest.iterchildren():
-        if not test.id in tests_by_id:
+        if test.id not in tests_by_id:
             test.remove()
 
     # Add tests that don't have expected data
diff --git a/tools/wptrunner/wptrunner/stability.py b/tools/wptrunner/wptrunner/stability.py
index 6eb060485c2cae..e1709c5749a433 100644
--- a/tools/wptrunner/wptrunner/stability.py
+++ b/tools/wptrunner/wptrunner/stability.py
@@ -274,6 +274,6 @@ def check_stability(logger, repeat_loop=10, repeat_restart=5, chaos_mode=True, m
             write_summary(logger, step_results, "FAIL")
             return 1
 
-        step_results.append((desc,  "PASS"))
+        step_results.append((desc, "PASS"))
 
     write_summary(logger, step_results, "PASS")
diff --git a/tools/wptrunner/wptrunner/testloader.py b/tools/wptrunner/wptrunner/testloader.py
index 0eb78bb884f6d3..199ed6c2666868 100644
--- a/tools/wptrunner/wptrunner/testloader.py
+++ b/tools/wptrunner/wptrunner/testloader.py
@@ -93,7 +93,7 @@ def __init__(self, path):
         for i, (test_type, test_path, tests) in enumerate(manifest_items):
             test_dir = tuple(os.path.split(test_path)[0].split(os.path.sep)[:3])
 
-            if not test_dir in by_dir:
+            if test_dir not in by_dir:
                 by_dir[test_dir] = PathData(test_dir)
 
             data = by_dir[test_dir]
@@ -261,7 +261,7 @@ def popleft(self):
                 return self.paths.popleft()
 
             @property
-            def badness(self_):
+            def badness(self_):  # noqa: N805
                 """Badness metric for this chunk"""
                 return self._badness(self_.time)
 
@@ -587,6 +587,7 @@ def __init__(self, test_queue):
         self.current_metadata = None
 
     @abstractmethod
+    # noqa: N805
     #@classmethod (doesn't compose with @abstractmethod)
     def make_queue(cls, tests, **kwargs):
         pass
diff --git a/tools/wptrunner/wptrunner/testrunner.py b/tools/wptrunner/wptrunner/testrunner.py
index 75f4825f95255c..85ffbe3741ab26 100644
--- a/tools/wptrunner/wptrunner/testrunner.py
+++ b/tools/wptrunner/wptrunner/testrunner.py
@@ -195,7 +195,7 @@ def init(self):
             self.logger.debug("Starting browser with settings %r" % self.browser_settings)
             self.browser.start(**self.browser_settings)
             self.browser_pid = self.browser.pid()
-        except:
+        except Exception:
             self.logger.warning("Failure during init %s" % traceback.format_exc())
             if self.init_timer is not None:
                 self.init_timer.cancel()
@@ -566,7 +566,7 @@ def test_ended(self, test, results):
         expected = test.expected()
         status = file_result.status if file_result.status != "EXTERNAL-TIMEOUT" else "TIMEOUT"
 
-        if file_result.status in  ("TIMEOUT", "EXTERNAL-TIMEOUT"):
+        if file_result.status in ("TIMEOUT", "EXTERNAL-TIMEOUT"):
             if self.browser.check_for_crashes():
                 status = "CRASH"
 
@@ -585,8 +585,8 @@ def test_ended(self, test, results):
 
         restart_before_next = (test.restart_after or
                                file_result.status in ("CRASH", "EXTERNAL-TIMEOUT") or
-                               ((subtest_unexpected or is_unexpected)
-                                and self.restart_on_unexpected))
+                               ((subtest_unexpected or is_unexpected) and
+                                self.restart_on_unexpected))
 
         if (self.pause_after_test or
             (self.pause_on_unexpected and (subtest_unexpected or is_unexpected))):
@@ -689,7 +689,7 @@ def cleanup(self):
                 break
             else:
                 if cmd == "log":
-                     self.log(*data)
+                    self.log(*data)
                 else:
                     self.logger.warning("%r: %r" % (cmd, data))
         while True:
diff --git a/tools/wptrunner/wptrunner/tests/test_hosts.py b/tools/wptrunner/wptrunner/tests/test_hosts.py
index 808b81606aeb51..e7d41f3b42081a 100644
--- a/tools/wptrunner/wptrunner/tests/test_hosts.py
+++ b/tools/wptrunner/wptrunner/tests/test_hosts.py
@@ -42,15 +42,13 @@ def test_alignment(self):
 192.168.1.1 another_host    another_alias
 ""","""127.0.0.1   localhost    alias
 192.168.1.1 another_host another_alias
-"""
-)
+""")
 
     def test_multiple_same_name(self):
         # The semantics are that we overwrite earlier entries with the same name
         self.do_test("""127.0.0.1    \tlocalhost  alias
 192.168.1.1 localhost    another_alias""","""192.168.1.1 localhost another_alias
-"""
-)
+""")
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/tools/wptrunner/wptrunner/update/__init__.py b/tools/wptrunner/wptrunner/update/__init__.py
index 497cb34ad0cb2e..99dac6bcccca7e 100644
--- a/tools/wptrunner/wptrunner/update/__init__.py
+++ b/tools/wptrunner/wptrunner/update/__init__.py
@@ -44,4 +44,3 @@ def main():
     assert structuredlog.get_default_logger() is not None
     success = run_update(logger, **args)
     sys.exit(0 if success else 1)
-
diff --git a/tools/wptrunner/wptrunner/update/sync.py b/tools/wptrunner/wptrunner/update/sync.py
index c1bff8543498a1..f2660e5a33ec3a 100644
--- a/tools/wptrunner/wptrunner/update/sync.py
+++ b/tools/wptrunner/wptrunner/update/sync.py
@@ -109,7 +109,7 @@ def create(self, state):
                          state.sync["branch"],
                          state.local_branch)
         sync_path = os.path.abspath(sync_tree.root)
-        if not sync_path in sys.path:
+        if sync_path not in sys.path:
             from update import setup_paths
             setup_paths(sync_path)
 
diff --git a/tools/wptrunner/wptrunner/update/tree.py b/tools/wptrunner/wptrunner/update/tree.py
index 01df0b4f94a33f..279ddba1f6f3d6 100644
--- a/tools/wptrunner/wptrunner/update/tree.py
+++ b/tools/wptrunner/wptrunner/update/tree.py
@@ -75,7 +75,7 @@ def is_type(cls, path=None):
             kwargs["repo"] = path
         try:
             hg("root", **kwargs)
-        except:
+        except Exception:
             return False
         return True
 
@@ -155,7 +155,7 @@ def is_type(cls, path=None):
             kwargs["repo"] = path
         try:
             git("rev-parse", "--show-toplevel", **kwargs)
-        except:
+        except Exception:
             return False
         return True
 
@@ -305,8 +305,8 @@ def clean(self):
 
     def paths(self):
         """List paths in the tree"""
-        repo_paths = [self.root] +  [os.path.join(self.root, path)
-                                     for path in self.submodules()]
+        repo_paths = [self.root] + [os.path.join(self.root, path)
+                                    for path in self.submodules()]
 
         rv = []
 
diff --git a/tools/wptrunner/wptrunner/vcs.py b/tools/wptrunner/wptrunner/vcs.py
index 16d53afc8be624..a51312d3937a05 100644
--- a/tools/wptrunner/wptrunner/vcs.py
+++ b/tools/wptrunner/wptrunner/vcs.py
@@ -15,7 +15,7 @@ def inner(command, *args, **kwargs):
         repo = kwargs.pop("repo", None)
         log_error = kwargs.pop("log_error", True)
         if kwargs:
-            raise TypeError, kwargs
+            raise TypeError(kwargs)
 
         args = list(args)
 
diff --git a/tools/wptrunner/wptrunner/webdriver_server.py b/tools/wptrunner/wptrunner/webdriver_server.py
index fc853bfb97e63c..79d8681c42873c 100644
--- a/tools/wptrunner/wptrunner/webdriver_server.py
+++ b/tools/wptrunner/wptrunner/webdriver_server.py
@@ -72,7 +72,7 @@ def _run(self, block):
             "Waiting for server to become accessible: %s" % self.url)
         try:
             wait_for_service((self.host, self.port))
-        except:
+        except Exception:
             self.logger.error(
                 "WebDriver HTTP server was not accessible "
                 "within the timeout:\n%s" % traceback.format_exc())
@@ -125,8 +125,6 @@ def make_command(self):
 
 
 class ChromeDriverServer(WebDriverServer):
-    default_base_path = "/"
-
     def __init__(self, logger, binary="chromedriver", port=None,
                  base_path="", args=None):
         WebDriverServer.__init__(
@@ -138,8 +136,6 @@ def make_command(self):
                 cmd_arg("url-base", self.base_path) if self.base_path else ""] + self._args
 
 class EdgeDriverServer(WebDriverServer):
-    default_base_path = "/"
-
     def __init__(self, logger, binary="microsoftwebdriver.exe", port=None,
                  base_path="", args=None):
         WebDriverServer.__init__(
@@ -157,17 +153,6 @@ def __init__(self, logger, binary="operadriver", port=None,
             self, logger, binary, port=port, base_path=base_path, args=args)
 
 
-class EdgeDriverServer(WebDriverServer):
-    def __init__(self, logger, binary="MicrosoftWebDriver.exe", port=None,
-                 base_path="", host="localhost", args=None):
-        WebDriverServer.__init__(
-            self, logger, binary, host=host, port=port, args=args)
-
-    def make_command(self):
-        return [self.binary,
-                "--port=%s" % str(self.port)] + self._args
-
-
 class InternetExplorerDriverServer(WebDriverServer):
     def __init__(self, logger, binary="IEDriverServer.exe", port=None,
                  base_path="", host="localhost", args=None):
diff --git a/tools/wptrunner/wptrunner/wptcommandline.py b/tools/wptrunner/wptrunner/wptcommandline.py
index b232462d915ab5..ad18e424cd5635 100644
--- a/tools/wptrunner/wptrunner/wptcommandline.py
+++ b/tools/wptrunner/wptrunner/wptcommandline.py
@@ -28,7 +28,7 @@ def require_arg(kwargs, name, value_func=None):
     if value_func is None:
         value_func = lambda x: x is not None
 
-    if not name in kwargs or not value_func(kwargs[name]):
+    if name not in kwargs or not value_func(kwargs[name]):
         print >> sys.stderr, "Missing required argument %s" % name
         sys.exit(1)
 
@@ -97,7 +97,8 @@ def create_parser(product_choices=None):
     test_selection_group.add_argument("--skip-timeout", action="store_true",
                                       help="Skip tests that are expected to time out")
     test_selection_group.add_argument("--tag", action="append", dest="tags",
-                                      help="Labels applied to tests to include in the run. Labels starting dir: are equivalent to top-level directories.")
+                                      help="Labels applied to tests to include in the run. "
+                                           "Labels starting dir: are equivalent to top-level directories.")
 
     debugging_group = parser.add_argument_group("Debugging")
     debugging_group.add_argument('--debugger', const="__default__", nargs="?",
@@ -479,7 +480,8 @@ def create_parser_update(product_choices=None):
                         help="Don't create a VCS commit containing the changes.")
     parser.add_argument("--sync", dest="sync", action="store_true", default=False,
                         help="Sync the tests with the latest from upstream (implies --patch)")
-    parser.add_argument("--ignore-existing", action="store_true", help="When updating test results only consider results from the logfiles provided, not existing expectations.")
+    parser.add_argument("--ignore-existing", action="store_true",
+                        help="When updating test results only consider results from the logfiles provided, not existing expectations.")
     parser.add_argument("--stability", nargs="?", action="store", const="unstable", default=None,
         help=("Reason for disabling tests. When updating test results, disable tests that have "
               "inconsistent results across many runs with the given reason."))
diff --git a/tools/wptrunner/wptrunner/wptmanifest/tests/test_serializer.py b/tools/wptrunner/wptrunner/wptmanifest/tests/test_serializer.py
index 6db2cbbbb477b4..6908ea4c1e020d 100644
--- a/tools/wptrunner/wptrunner/wptmanifest/tests/test_serializer.py
+++ b/tools/wptrunner/wptrunner/wptmanifest/tests/test_serializer.py
@@ -211,15 +211,15 @@ def test_escape_11(self):
 """)
 
     def test_atom_1(self):
-            self.compare(r"""key: @True
+        self.compare(r"""key: @True
 """)
 
     def test_atom_2(self):
-            self.compare(r"""key: @False
+        self.compare(r"""key: @False
 """)
 
     def test_atom_3(self):
-            self.compare(r"""key: @Reset
+        self.compare(r"""key: @Reset
 """)
 
     def test_atom_4(self):
diff --git a/tools/wptrunner/wptrunner/wptmanifest/tests/test_tokenizer.py b/tools/wptrunner/wptrunner/wptmanifest/tests/test_tokenizer.py
index 88176c5a169052..a64ce0c7bb7d8d 100644
--- a/tools/wptrunner/wptrunner/wptmanifest/tests/test_tokenizer.py
+++ b/tools/wptrunner/wptrunner/wptmanifest/tests/test_tokenizer.py
@@ -145,8 +145,7 @@ def test_key_14(self):
                       (token_types.string, r"\nb")])
 
     def test_list_0(self):
-        self.compare(
-"""
+        self.compare("""
 key: []""",
             [(token_types.string, "key"),
              (token_types.separator, ":"),
@@ -154,8 +153,7 @@ def test_list_0(self):
              (token_types.list_end, "]")])
 
     def test_list_1(self):
-        self.compare(
-"""
+        self.compare("""
 key: [a, "b"]""",
             [(token_types.string, "key"),
              (token_types.separator, ":"),
@@ -165,8 +163,7 @@ def test_list_1(self):
              (token_types.list_end, "]")])
 
     def test_list_2(self):
-        self.compare(
-"""
+        self.compare("""
 key: [a,
       b]""",
             [(token_types.string, "key"),
@@ -177,8 +174,7 @@ def test_list_2(self):
              (token_types.list_end, "]")])
 
     def test_list_3(self):
-        self.compare(
-"""
+        self.compare("""
 key: [a, #b]
       c]""",
             [(token_types.string, "key"),
@@ -199,18 +195,16 @@ def test_list_5(self):
             c]""")
 
     def test_list_6(self):
-        self.compare(
-"""key: [a , b]""",
-        [(token_types.string, "key"),
-         (token_types.separator, ":"),
-         (token_types.list_start, "["),
-         (token_types.string, "a"),
-         (token_types.string, "b"),
-         (token_types.list_end, "]")])
+        self.compare("""key: [a , b]""",
+            [(token_types.string, "key"),
+             (token_types.separator, ":"),
+             (token_types.list_start, "["),
+             (token_types.string, "a"),
+             (token_types.string, "b"),
+             (token_types.list_end, "]")])
 
     def test_expr_0(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if cond == 1: value""",
             [(token_types.string, "key"),
@@ -224,8 +218,7 @@ def test_expr_0(self):
              (token_types.string, "value")])
 
     def test_expr_1(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if cond == 1: value1
   value2""",
@@ -241,8 +234,7 @@ def test_expr_1(self):
              (token_types.string, "value2")])
 
     def test_expr_2(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if cond=="1": value""",
             [(token_types.string, "key"),
@@ -256,8 +248,7 @@ def test_expr_2(self):
              (token_types.string, "value")])
 
     def test_expr_3(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if cond==1.1: value""",
             [(token_types.string, "key"),
@@ -271,8 +262,7 @@ def test_expr_3(self):
              (token_types.string, "value")])
 
     def test_expr_4(self):
-        self.compare(
-            """
+        self.compare("""
 key:
   if cond==1.1 and cond2 == "a": value""",
             [(token_types.string, "key"),
@@ -290,8 +280,7 @@ def test_expr_4(self):
              (token_types.string, "value")])
 
     def test_expr_5(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if (cond==1.1 ): value""",
             [(token_types.string, "key"),
@@ -307,8 +296,7 @@ def test_expr_5(self):
              (token_types.string, "value")])
 
     def test_expr_6(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if "\\ttest": value""",
             [(token_types.string, "key"),
@@ -322,27 +310,26 @@ def test_expr_6(self):
     def test_expr_7(self):
         with self.assertRaises(parser.ParseError):
             self.tokenize(
-"""
+                """
 key:
   if 1A: value""")
 
     def test_expr_8(self):
         with self.assertRaises(parser.ParseError):
             self.tokenize(
-"""
+                """
 key:
   if 1a: value""")
 
     def test_expr_9(self):
         with self.assertRaises(parser.ParseError):
             self.tokenize(
-"""
+                """
 key:
   if 1.1.1: value""")
 
     def test_expr_10(self):
-        self.compare(
-"""
+        self.compare("""
 key:
   if 1.: value""",
             [(token_types.string, "key"),
diff --git a/tools/wptrunner/wptrunner/wptrunner.py b/tools/wptrunner/wptrunner/wptrunner.py
index 637cbe57b6f458..6677902a49a66b 100644
--- a/tools/wptrunner/wptrunner/wptrunner.py
+++ b/tools/wptrunner/wptrunner/wptrunner.py
@@ -307,7 +307,8 @@ def main():
         return start(**kwargs)
     except Exception:
         if kwargs["pdb"]:
-            import pdb, traceback
+            import pdb
+            import traceback
             print traceback.format_exc()
             pdb.post_mortem()
         else:
diff --git a/tools/wptrunner/wptrunner/wpttest.py b/tools/wptrunner/wptrunner/wpttest.py
index d283e854205d58..9f4c1bed135536 100644
--- a/tools/wptrunner/wptrunner/wpttest.py
+++ b/tools/wptrunner/wptrunner/wpttest.py
@@ -356,7 +356,7 @@ def from_manifest(cls,
         return node
 
     def update_metadata(self, metadata):
-        if not "url_count" in metadata:
+        if "url_count" not in metadata:
             metadata["url_count"] = defaultdict(int)
         for reference, _ in self.references:
             # We assume a naive implementation in which a url with multiple
diff --git a/tools/wptserve/wptserve/pipes.py b/tools/wptserve/wptserve/pipes.py
index 7203815b70ce42..b71c8afa309148 100644
--- a/tools/wptserve/wptserve/pipes.py
+++ b/tools/wptserve/wptserve/pipes.py
@@ -6,6 +6,7 @@
 import uuid
 from cStringIO import StringIO
 
+from six import text_type
 
 def resolve_content(response):
     return b"".join(item for item in response.iter_content(read_file=True))
@@ -276,18 +277,18 @@ def slice(request, response, start, end=None):
 
 
 class ReplacementTokenizer(object):
-    def ident(scanner, token):
+    def ident(self, token):
         return ("ident", token)
 
-    def index(scanner, token):
+    def index(self, token):
         token = token[1:-1]
         try:
             token = int(token)
         except ValueError:
-            token = unicode(token, "utf8")
+            token = token.decode('utf8')
         return ("index", token)
 
-    def var(scanner, token):
+    def var(self, token):
         token = token[:-1]
         return ("var", token)
 
@@ -425,7 +426,7 @@ def config_replacement(match):
 
         #Should possibly support escaping for other contexts e.g. script
         #TODO: read the encoding of the response
-        return escape_func(unicode(value)).encode("utf-8")
+        return escape_func(text_type(value)).encode("utf-8")
 
     template_regexp = re.compile(r"{{([^}]*)}}")
     new_content = template_regexp.sub(config_replacement, content)
diff --git a/tools/wptserve/wptserve/response.py b/tools/wptserve/wptserve/response.py
index 50ff00dde9440e..20b7b42699621e 100644
--- a/tools/wptserve/wptserve/response.py
+++ b/tools/wptserve/wptserve/response.py
@@ -9,6 +9,8 @@
 from .constants import response_codes
 from .logger import get_logger
 
+from six import string_types, binary_type, text_type
+
 missing = object()
 
 class Response(object):
@@ -400,7 +402,7 @@ def write_default_headers(self):
             if name.lower() not in self._headers_seen:
                 self.write_header(name, f())
 
-        if (type(self._response.content) in (str, unicode) and
+        if (isinstance(self._response.content, string_types) and
             "content-length" not in self._headers_seen):
             #Would be nice to avoid double-encoding here
             self.write_header("Content-Length", len(self.encode(self._response.content)))
@@ -457,9 +459,9 @@ def write_content_file(self, data):
 
     def encode(self, data):
         """Convert unicode to bytes according to response.encoding."""
-        if isinstance(data, str):
+        if isinstance(data, binary_type):
             return data
-        elif isinstance(data, unicode):
+        elif isinstance(data, text_type):
             return data.encode(self._response.encoding)
         else:
             raise ValueError
diff --git a/tools/wptserve/wptserve/server.py b/tools/wptserve/wptserve/server.py
index 2a83bd8097ef2d..f9ed238624b511 100644
--- a/tools/wptserve/wptserve/server.py
+++ b/tools/wptserve/wptserve/server.py
@@ -110,14 +110,15 @@ class WebTestServer(ThreadingMixIn, BaseHTTPServer.HTTPServer):
     # Ensure that we don't hang on shutdown waiting for requests
     daemon_threads = True
 
-    def __init__(self, server_address, RequestHandlerClass, router, rewriter, bind_hostname,
+    def __init__(self, server_address, request_handler_cls,
+                 router, rewriter, bind_hostname,
                  config=None, use_ssl=False, key_file=None, certificate=None,
                  encrypt_after_connect=False, latency=None, **kwargs):
         """Server for HTTP(s) Requests
 
         :param server_address: tuple of (server_name, port)
 
-        :param RequestHandlerClass: BaseHTTPRequestHandler-like class to use for
+        :param request_handler_cls: BaseHTTPRequestHandler-like class to use for
                                     handling requests.
 
         :param router: Router instance to use for matching requests to handler
@@ -161,7 +162,7 @@ def __init__(self, server_address, RequestHandlerClass, router, rewriter, bind_h
             hostname_port = ("",server_address[1])
 
         #super doesn't work here because BaseHTTPServer.HTTPServer is old-style
-        BaseHTTPServer.HTTPServer.__init__(self, hostname_port, RequestHandlerClass, **kwargs)
+        BaseHTTPServer.HTTPServer.__init__(self, hostname_port, request_handler_cls, **kwargs)
 
         if config is not None:
             Server.config = config