--- a/testing/awsy/awsy/process_perf_data.py
+++ b/testing/awsy/awsy/process_perf_data.py
@@ -1,15 +1,16 @@
 #!/usr/bin/env python
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from __future__ import absolute_import, division, print_function
 
+import six
 import os
 import sys
 import json
 import math
 import glob
 
 AWSY_PATH = os.path.dirname(os.path.realpath(__file__))
 if AWSY_PATH not in sys.path:
@@ -156,17 +157,17 @@ def create_suite(
             # with RSS + USS of e10s).
             totals_rss = parse_about_memory.calculate_memory_report_values(
                 memory_report_path, node, ["Main"]
             )
             totals_uss = parse_about_memory.calculate_memory_report_values(
                 memory_report_path, "resident-unique"
             )
             value = list(totals_rss.values())[0] + sum(
-                [v for k, v in totals_uss.iteritems() if "Main" not in k]
+                [v for k, v in six.iteritems(totals_uss) if "Main" not in k]
             )
 
         subtest = {
             "name": checkpoint["name"],
             "value": value,
             "lowerIsBetter": True,
             "unit": "bytes",
         }

--- a/testing/awsy/mach_commands.py
+++ b/testing/awsy/mach_commands.py
@@ -183,17 +183,17 @@ class MachCommands(MachCommandBase):
                 #   Name.app/Contents/MacOS/libdmd.dylib
                 #   Name.app/Contents/Resources/dmd.py
                 bin_dir = os.path.join(bin_dir, "../Resources/")
 
             # Also add the bin dir to the python path so we can use dmd.py
             if bin_dir not in sys.path:
                 sys.path.append(bin_dir)
 
-        for k, v in kwargs.iteritems():
+        for k, v in six.iteritems(kwargs):
             setattr(args, k, v)
 
         parser.verify_usage(args)
 
         args.logger = commandline.setup_logging(
             "Are We Slim Yet Tests", args, {"mach": sys.stdout}
         )
         failed = MarionetteHarness(MarionetteTestRunner, args=vars(args)).run()

--- a/testing/firefox-ui/mach_commands.py
+++ b/testing/firefox-ui/mach_commands.py
@@ -1,14 +1,15 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from __future__ import absolute_import, unicode_literals
 
+import six
 import logging
 import os
 import sys
 
 from mozbuild.base import (
     MachCommandBase,
     MachCommandConditions as conditions,
     BinaryNotFoundException,
@@ -68,17 +69,17 @@ def run_firefox_ui_test(testtype=None, t
     kwargs["logger"] = kwargs.pop("log", None)
     if not kwargs["logger"]:
         kwargs["logger"] = commandline.setup_logging(
             "Firefox UI - {} Tests".format(testtype), {"mach": sys.stdout}
         )
 
     args = Namespace()
 
-    for k, v in kwargs.iteritems():
+    for k, v in six.iteritems(kwargs):
         setattr(args, k, v)
 
     parser.verify_usage(args)
 
     failed = test_types[testtype]["cli_module"].cli(args=vars(args))
 
     if failed > 0:
         return 1

--- a/testing/mochitest/mach_test_package_commands.py
+++ b/testing/mochitest/mach_test_package_commands.py
@@ -1,14 +1,14 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from __future__ import absolute_import, unicode_literals
-
+import six
 import json
 import os
 import sys
 from argparse import Namespace
 from functools import partial
 
 from mach.decorators import (
     CommandProvider,
@@ -27,17 +27,17 @@ def run_test(context, is_junit, **kwargs
 
     if not kwargs.get("log"):
         kwargs["log"] = setup_logging("mochitest", kwargs, {"mach": sys.stdout})
     global logger
     logger = kwargs["log"]
 
     flavor = kwargs.get("flavor") or "mochitest"
     if flavor not in ALL_FLAVORS:
-        for fname, fobj in ALL_FLAVORS.iteritems():
+        for fname, fobj in six.iteritems(ALL_FLAVORS):
             if flavor in fobj["aliases"]:
                 flavor = fname
                 break
     fobj = ALL_FLAVORS[flavor]
     kwargs.update(fobj.get("extra_args", {}))
 
     if kwargs.get("allow_software_gl_layers"):
         os.environ["MOZ_LAYERS_ALLOW_SOFTWARE_GL"] = "1"

--- a/testing/mozbase/docs/_static/structured_example.py
+++ b/testing/mozbase/docs/_static/structured_example.py
@@ -1,14 +1,15 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from __future__ import absolute_import
 
+import six
 import argparse
 import sys
 import traceback
 import types
 
 from mozlog import commandline, get_default_logger
 
 
@@ -50,17 +51,17 @@ def test_expected_fail():
     assert_equals(2 + 2, 5)
 
 
 class TestRunner(object):
     def __init__(self):
         self.logger = get_default_logger(component="TestRunner")
 
     def gather_tests(self):
-        for item in globals().itervalues():
+        for item in six.itervalues(globals()):
             if isinstance(item, types.FunctionType) and item.__name__.startswith(
                 "test_"
             ):
                 yield item.__name__, item
 
     def run(self):
         tests = list(self.gather_tests())
 

--- a/testing/mozharness/mozharness/base/script.py
+++ b/testing/mozharness/mozharness/base/script.py
@@ -1411,17 +1411,17 @@ class ScriptMixin(PlatformMixin):
         repl_dict = {}
         if hasattr(self.script_obj, "query_abs_dirs"):
             # allow for 'make': '%(abs_work_dir)s/...' etc.
             dirs = self.script_obj.query_abs_dirs()
             repl_dict.update(dirs)
         if isinstance(exe, dict):
             found = False
             # allow for searchable paths of the exe
-            for name, path in exe.iteritems():
+            for name, path in six.iteritems(exe):
                 if isinstance(path, list) or isinstance(path, tuple):
                     path = [x % repl_dict for x in path]
                     if all([os.path.exists(section) for section in path]):
                         found = True
                 elif isinstance(path, str):
                     path = path % repl_dict
                     if os.path.exists(path):
                         found = True

--- a/testing/mozharness/mozharness/mozilla/testing/try_tools.py
+++ b/testing/mozharness/mozharness/mozilla/testing/try_tools.py
@@ -1,16 +1,17 @@
 #!/usr/bin/env python
 # ***** BEGIN LICENSE BLOCK *****
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
 # You can obtain one at http://mozilla.org/MPL/2.0/.
 # ***** END LICENSE BLOCK *****
 
 from __future__ import absolute_import
+import six
 import argparse
 import os
 import re
 from collections import defaultdict
 
 from mozharness.base.script import PostScriptAction
 from mozharness.base.transfer import TransferMixin
 
@@ -153,17 +154,17 @@ class TryToolsMixin(TransferMixin):
 
         label_dict = {}
 
         def label_from_val(val):
             if val in label_dict:
                 return label_dict[val]
             return "--%s" % val.replace("_", "-")
 
-        for label, (opts, _) in self.known_try_arguments.iteritems():
+        for label, (opts, _) in six.iteritems(self.known_try_arguments):
             if "action" in opts and opts["action"] not in (
                 "append",
                 "store",
                 "store_true",
                 "store_false",
             ):
                 self.fatal(
                     "Try syntax does not support passing custom or store_const "
@@ -178,17 +179,17 @@ class TryToolsMixin(TransferMixin):
         (args, _) = parser.parse_known_args(all_try_args)
         self.try_test_paths = self._group_test_paths(args.try_test_paths)
         del args.try_test_paths
 
         out_args = defaultdict(list)
         # This is a pretty hacky way to echo arguments down to the harness.
         # Hopefully this can be improved once we have a configuration system
         # in tree for harnesses that relies less on a command line.
-        for arg, value in vars(args).iteritems():
+        for arg, value in six.iteritems(vars(args)):
             if value:
                 label = label_from_val(arg)
                 _, flavors = self.known_try_arguments[label]
 
                 for f in flavors:
                     if isinstance(value, bool):
                         # A store_true or store_false argument.
                         out_args[f].append(label)

--- a/testing/raptor/raptor/cmdline.py
+++ b/testing/raptor/raptor/cmdline.py
@@ -1,13 +1,14 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
 # You can obtain one at http://mozilla.org/MPL/2.0/.
 from __future__ import absolute_import, print_function
 
+import six
 import argparse
 import os
 import platform
 
 from mozlog.commandline import add_logging_group
 
 (FIREFOX, CHROME, CHROMIUM) = DESKTOP_APPS = ["firefox", "chrome", "chromium"]
 (FENNEC, GECKOVIEW, REFBROW, FENIX, CHROME_ANDROID) = FIREFOX_ANDROID_APPS = [
@@ -601,17 +602,17 @@ class _PrintTests(_StopAction):
                     if next_test["type"] == "pageload":
                         subtest = next_test["name"]
                         measure = next_test.get("measure")
                         if measure is not None:
                             subtest = "{0} ({1})".format(subtest, measure)
                         test_list[suite]["subtests"].append(subtest)
 
             # print the list in a nice, readable format
-            for key in sorted(test_list.iterkeys()):
+            for key in sorted(six.iterkeys(test_list)):
                 print("\n%s" % key)
                 print("  type: %s" % test_list[key]["type"])
                 if len(test_list[key]["subtests"]) != 0:
                     print("  subtests:")
                     for _sub in sorted(test_list[key]["subtests"]):
                         print("    %s" % _sub)
 
         print("\nDone.")

--- a/testing/raptor/raptor/output.py
+++ b/testing/raptor/raptor/output.py
@@ -2,16 +2,17 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 # some parts of this originally taken from /testing/talos/talos/output.py
 
 """output raptor test results"""
 from __future__ import absolute_import, division, print_function
 
+import six
 import filters
 
 import json
 import os
 
 from abc import ABCMeta, abstractmethod
 from logger.logger import RaptorLogger
 
@@ -628,17 +629,17 @@ class PerftestOutput(object):
                 if name in self.subtest_alert_on:
                     LOG.info(
                         "turning on subtest alerting for measurement type: %s" % name
                     )
                     _subtests[name]["shouldAlert"] = True
 
         failed_tests = []
         for pagecycle in data:
-            for _sub, _value in pagecycle[0].iteritems():
+            for _sub, _value in six.iteritems(pagecycle[0]):
                 if _value["decodedFrames"] == 0:
                     failed_tests.append(
                         "%s test Failed. decodedFrames %s droppedFrames %s."
                         % (_sub, _value["decodedFrames"], _value["droppedFrames"])
                     )
 
                 try:
                     percent_dropped = (

--- a/testing/raptor/raptor/results.py
+++ b/testing/raptor/raptor/results.py
@@ -1,16 +1,17 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 # class to process, format, and report raptor test results
 # received from the raptor control server
 from __future__ import absolute_import
 
+import six
 import json
 import os
 
 from abc import ABCMeta, abstractmethod
 from logger.logger import RaptorLogger
 from output import RaptorOutput, BrowsertimeOutput
 
 LOG = RaptorLogger(component="perftest-results-handler")
@@ -786,17 +787,19 @@ class BrowsertimeResultsHandler(Perftest
                 elif test["type"] == "pageload":
                     self.results.append(_new_pageload_result(new_result))
                 elif test["type"] == "benchmark":
                     for i, item in enumerate(self.results):
                         if item["name"] == test["name"] and not _is_supporting_data(
                             item
                         ):
                             # add page cycle custom measurements to the existing results
-                            for measurement in new_result["measurements"].iteritems():
+                            for measurement in six.iteritems(
+                                new_result["measurements"]
+                            ):
                                 self.results[i]["measurements"][measurement[0]].extend(
                                     measurement[1]
                                 )
                             break
                     else:
                         self.results.append(_new_benchmark_result(new_result))
 
         # now have all results gathered from all browsertime test URLs; format them for output

--- a/testing/tps/create_venv.py
+++ b/testing/tps/create_venv.py
@@ -6,16 +6,17 @@
 """
 This scripts sets up a virtualenv and installs TPS into it.
 It's probably best to specify a path NOT inside the repo, otherwise
 all the virtualenv files will show up in e.g. hg status.
 """
 
 from __future__ import absolute_import, print_function
 
+import six
 import optparse
 import os
 import shutil
 import subprocess
 import sys
 import urllib2
 import zipfile
 
@@ -92,17 +93,17 @@ def setup_virtualenv(target, python_bin=
         shutil.rmtree(os.path.dirname(script_path), ignore_errors=True)
 
 
 def update_configfile(source, target, replacements):
     lines = []
 
     with open(source) as config:
         for line in config:
-            for source_string, target_string in replacements.iteritems():
+            for source_string, target_string in six.iteritems(replacements):
                 if target_string:
                     line = line.replace(source_string, target_string)
             lines.append(line)
 
     with open(target, "w") as config:
         for line in lines:
             config.write(line)