--- a/testing/marionette/client/docs/conf.py
+++ b/testing/marionette/client/docs/conf.py
@@ -6,16 +6,18 @@
 # This file is execfile()d with the current directory set to its containing dir.
 #
 # Note that not all possible configuration values are present in this
 # autogenerated file.
 #
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
+from __future__ import absolute_import
+
 import os
 import sys
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 # sys.path.insert(0, os.path.abspath('.'))
 

--- a/testing/marionette/client/marionette_driver/__init__.py
+++ b/testing/marionette/client/marionette_driver/__init__.py
@@ -1,14 +1,16 @@
 # 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/.
 
 __version__ = '2.5.0'
 
+from __future__ import absolute_import
+
 from marionette_driver import (
     addons,
     by,
     date_time_value,
     decorators,
     errors,
     expected,
     geckoinstance,

--- a/testing/marionette/client/marionette_driver/addons.py
+++ b/testing/marionette/client/marionette_driver/addons.py
@@ -1,12 +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
+
 from . import errors
 
 __all__ = ["Addons", "AddonInstallException"]
 
 
 class AddonInstallException(errors.MarionetteException):
     pass
 

--- a/testing/marionette/client/marionette_driver/by.py
+++ b/testing/marionette/client/marionette_driver/by.py
@@ -8,16 +8,18 @@
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import
+
 
 class By(object):
     ID = "id"
     XPATH = "xpath"
     LINK_TEXT = "link text"
     PARTIAL_LINK_TEXT = "partial link text"
     NAME = "name"
     TAG_NAME = "tag name"

--- a/testing/marionette/client/marionette_driver/date_time_value.py
+++ b/testing/marionette/client/marionette_driver/date_time_value.py
@@ -1,12 +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
+
 
 class DateTimeValue(object):
     """
     Interface for setting the value of HTML5 "date" and "time" input elements.
 
     Simple usage example:
 
     ::

--- a/testing/marionette/client/marionette_driver/decorators.py
+++ b/testing/marionette/client/marionette_driver/decorators.py
@@ -1,12 +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/.
 
+from __future__ import (
+    absolute_import,
+    print_function
+)
+
 from functools import wraps
 import socket
 
 
 def _find_marionette_in_args(*args, **kwargs):
     try:
         m = [a for a in args + tuple(kwargs.values()) if hasattr(a, 'session')][0]
     except IndexError:

--- a/testing/marionette/client/marionette_driver/errors.py
+++ b/testing/marionette/client/marionette_driver/errors.py
@@ -1,12 +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
+
 import traceback
 
 
 class MarionetteException(Exception):
 
     """Raised when a generic non-recoverable exception has occured."""
 
     status = "webdriver error"

--- a/testing/marionette/client/marionette_driver/expected.py
+++ b/testing/marionette/client/marionette_driver/expected.py
@@ -1,12 +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
+
 import errors
 import types
 
 from marionette import HTMLElement
 
 """This file provides a set of expected conditions for common use
 cases when writing Marionette tests.
 

--- a/testing/marionette/client/marionette_driver/geckoinstance.py
+++ b/testing/marionette/client/marionette_driver/geckoinstance.py
@@ -1,12 +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
+
 import os
 import sys
 import tempfile
 import time
 
 from copy import deepcopy
 
 import mozversion
@@ -204,17 +206,17 @@ class GeckoInstance(object):
             if not app and kwargs["bin"] is not None:
                 app_id = mozversion.get_version(binary=kwargs["bin"])["application_id"]
                 app = app_ids[app_id]
 
             instance_class = apps[app]
         except (IOError, KeyError):
             exc, val, tb = sys.exc_info()
             msg = 'Application "{0}" unknown (should be one of {1})'
-            raise NotImplementedError, msg.format(app, apps.keys()), tb
+            raise NotImplementedError(msg.format(app, apps.keys()), tb)
 
         return instance_class(*args, **kwargs)
 
     def start(self):
         self._update_profile()
         self.runner = self.runner_class(**self._get_runner_args())
         self.runner.start()
 
@@ -347,17 +349,17 @@ class FennecInstance(GeckoInstance):
         self.runner = self.runner_class(**self._get_runner_args())
         try:
             if self.connect_to_running_emulator:
                 self.runner.device.connect()
             self.runner.start()
         except Exception as e:
             exc, val, tb = sys.exc_info()
             message = "Error possibly due to runner or device args: {}"
-            raise exc, message.format(e.message), tb
+            raise (exc, message.format(e.message), tb)
         # gecko_log comes from logcat when running with device/emulator
         logcat_args = {
             "filterspec": "Gecko",
             "serial": self.runner.device.dm._deviceSerial
         }
         if self.gecko_log == "-":
             logcat_args["stream"] = sys.stdout
         else:

--- a/testing/marionette/client/marionette_driver/gestures.py
+++ b/testing/marionette/client/marionette_driver/gestures.py
@@ -1,12 +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
+
 from marionette import MultiActions, Actions
 
 
 def smooth_scroll(marionette_session, start_element, axis, direction,
                   length, increments=None, wait_period=None, scroll_back=None):
     """
         :param axis:  y or x
         :param direction: 0 for positive, and -1 for negative

--- a/testing/marionette/client/marionette_driver/keys.py
+++ b/testing/marionette/client/marionette_driver/keys.py
@@ -8,16 +8,18 @@
 #     http //www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing software
 # distributed under the License is distributed on an "AS IS" BASIS
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import
+
 
 class Keys(object):
 
     NULL = u'\ue000'
     CANCEL = u'\ue001'  # ^break
     HELP = u'\ue002'
     BACK_SPACE = u'\ue003'
     TAB = u'\ue004'

--- a/testing/marionette/client/marionette_driver/localization.py
+++ b/testing/marionette/client/marionette_driver/localization.py
@@ -1,12 +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
+
 
 class L10n(object):
     """An API which allows Marionette to handle localized content.
 
     The `localization`_ of UI elements in Gecko based applications is done via
     entities and properties. For static values entities are used, which are located
     in .dtd files. Whereby for dynamically updated content the values come from
     .property files. Both types of elements can be identifed via a unique id,

--- a/testing/marionette/client/marionette_driver/marionette.py
+++ b/testing/marionette/client/marionette_driver/marionette.py
@@ -1,12 +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
+
 import base64
 import datetime
 import json
 import os
 import socket
 import sys
 import time
 import traceback
@@ -634,17 +636,17 @@ class Marionette(object):
         except socket.timeout:
             # Something went wrong with starting up Marionette server. Given
             # that the process will not quit itself, force a shutdown immediately.
             self.cleanup()
 
             msg = "Process killed after {}s because no connection to Marionette "\
                   "server could be established. Check gecko.log for errors"
             _, _, tb = sys.exc_info()
-            raise IOError, msg.format(timeout), tb
+            raise IOError(msg.format(timeout), tb)
 
     def cleanup(self):
         if self.session is not None:
             try:
                 self.delete_session()
             except (errors.MarionetteException, IOError):
                 # These exceptions get thrown if the Marionette server
                 # hit an exception/died or the connection died. We can
@@ -788,17 +790,17 @@ class Marionette(object):
         frame, and is only called via the `@do_process_check` decorator.
 
         """
         exc, val, tb = sys.exc_info()
 
         # If the application hasn't been launched by Marionette no further action can be done.
         # In such cases we simply re-throw the exception.
         if not self.instance:
-            raise exc, val, tb
+            raise(exc, val, tb)
 
         else:
             # Somehow the socket disconnected. Give the application some time to shutdown
             # itself before killing the process.
             returncode = self.instance.runner.wait(timeout=self.DEFAULT_SHUTDOWN_TIMEOUT)
 
             if returncode is None:
                 message = ('Process killed because the connection to Marionette server is '
@@ -816,17 +818,17 @@ class Marionette(object):
                         message = 'Process crashed (Exit code: {returncode})'
                 else:
                     message = 'Process has been unexpectedly closed (Exit code: {returncode})'
 
                 self.delete_session(send_request=False, reset_session_id=True)
 
             message += ' (Reason: {reason})'
 
-            raise IOError, message.format(returncode=returncode, reason=val), tb
+            raise IOError(message.format(returncode=returncode, reason=val), tb)
 
     @staticmethod
     def convert_keys(*string):
         typing = []
         for val in string:
             if isinstance(val, Keys):
                 typing.append(val)
             elif isinstance(val, int):
@@ -1146,17 +1148,17 @@ class Marionette(object):
 
             try:
                 timeout = self.DEFAULT_SHUTDOWN_TIMEOUT + self.DEFAULT_STARTUP_TIMEOUT
                 self.raise_for_port(timeout=timeout)
             except socket.timeout:
                 if self.instance.runner.returncode is not None:
                     exc, val, tb = sys.exc_info()
                     self.cleanup()
-                    raise exc, "Requested restart of the application was aborted", tb
+                    raise exc("Requested restart of the application was aborted", tb)
 
         else:
             self.delete_session()
             self.instance.restart(clean=clean)
             self.raise_for_port(timeout=self.DEFAULT_STARTUP_TIMEOUT)
 
         if cause not in (None, "restart"):
             raise errors.MarionetteException("Unexpected shutdown reason '{}' for "

--- a/testing/marionette/client/marionette_driver/selection.py
+++ b/testing/marionette/client/marionette_driver/selection.py
@@ -1,13 +1,15 @@
 # -*- coding: utf-8 -*-
 # 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
+
 
 class SelectionManager(object):
     '''Interface for manipulating the selection and carets of the element.
 
     We call the blinking cursor (nsCaret) as cursor, and call AccessibleCaret as
     caret for short.
 
     Simple usage example:

--- a/testing/marionette/client/marionette_driver/timeout.py
+++ b/testing/marionette/client/marionette_driver/timeout.py
@@ -1,13 +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 errors
 
 
 DEFAULT_SCRIPT_TIMEOUT = 30
 DEFAULT_PAGE_LOAD_TIMEOUT = 300
 DEFAULT_IMPLICIT_WAIT_TIMEOUT = 0
 
 

--- a/testing/marionette/client/marionette_driver/transport.py
+++ b/testing/marionette/client/marionette_driver/transport.py
@@ -1,12 +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
+
 import json
 import socket
 import sys
 import time
 
 
 class SocketTimeout(object):
     def __init__(self, socket, timeout):
@@ -199,17 +201,17 @@ class TcpTransport(object):
             with SocketTimeout(self._sock, 60.0):
                 # first packet is always a JSON Object
                 # which we can use to tell which protocol level we are at
                 raw = self.receive(unmarshal=False)
         except socket.timeout:
             msg = "Connection attempt failed because no data has been received over the socket: {}"
             exc, val, tb = sys.exc_info()
 
-            raise exc, msg.format(val), tb
+            raise exc(msg.format(val), tb)
 
         hello = json.loads(raw)
         application_type = hello.get("applicationType")
         protocol = hello.get("marionetteProtocol")
 
         if application_type != "gecko":
             raise ValueError("Application type '{}' is not supported".format(application_type))
 

--- a/testing/marionette/client/marionette_driver/wait.py
+++ b/testing/marionette/client/marionette_driver/wait.py
@@ -1,12 +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
+
 import collections
 import errors
 import sys
 import time
 
 DEFAULT_TIMEOUT = 5
 DEFAULT_INTERVAL = 0.1
 

--- a/testing/marionette/client/setup.py
+++ b/testing/marionette/client/setup.py
@@ -1,12 +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
+
 import os
 import re
 from setuptools import setup, find_packages
 
 THIS_DIR = os.path.dirname(os.path.realpath(__name__))
 
 
 def read(*parts):

--- a/testing/marionette/harness/marionette_harness/__init__.py
+++ b/testing/marionette/harness/marionette_harness/__init__.py
@@ -1,14 +1,16 @@
 # 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/.
 
 __version__ = '4.3.0'
 
+from __future__ import absolute_import
+
 from .marionette_test import (
     CommonTestCase,
     expectedFailure,
     MarionetteTestCase,
     parameterized,
     run_if_e10s,
     run_if_manage_instance,
     skip,

--- a/testing/marionette/harness/marionette_harness/marionette_test/__init__.py
+++ b/testing/marionette/harness/marionette_harness/marionette_test/__init__.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/.
 
 __version__ = '3.1.0'
 
+from __future__ import absolute_import
 
 from unittest.case import (
     expectedFailure,
     skip,
     SkipTest,
 )
 
 from .decorators import (

--- a/testing/marionette/harness/marionette_harness/marionette_test/decorators.py
+++ b/testing/marionette/harness/marionette_harness/marionette_test/decorators.py
@@ -1,12 +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
+
 import functools
 import types
 
 from unittest.case import (
     SkipTest,
 )
 
 

--- a/testing/marionette/harness/marionette_harness/marionette_test/testcases.py
+++ b/testing/marionette/harness/marionette_harness/marionette_test/testcases.py
@@ -1,12 +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
+
 import imp
 import re
 import sys
 import time
 import types
 import unittest
 import warnings
 import weakref

--- a/testing/marionette/harness/marionette_harness/runner/__init__.py
+++ b/testing/marionette/harness/marionette_harness/runner/__init__.py
@@ -1,12 +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
+
 from .base import (
     BaseMarionetteArguments,
     BaseMarionetteTestRunner,
     Marionette,
     MarionetteTest,
     MarionetteTestResult,
     MarionetteTextTestRunner,
     TestManifest,

--- a/testing/marionette/harness/marionette_harness/runner/base.py
+++ b/testing/marionette/harness/marionette_harness/runner/base.py
@@ -1,12 +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
+
 import json
 import os
 import random
 import re
 import socket
 import sys
 import time
 import traceback
@@ -651,17 +653,17 @@ class BaseMarionetteTestRunner(object):
                 if not os.path.exists(path):
                     raise IOError('--testvars file {} does not exist'.format(path))
                 try:
                     with open(path) as f:
                         data.append(json.loads(f.read()))
                 except ValueError as e:
                     exc, val, tb = sys.exc_info()
                     msg = "JSON file ({0}) is not properly formatted: {1}"
-                    raise exc, msg.format(os.path.abspath(path), e.message), tb
+                    raise exc(msg.format(os.path.abspath(path), e.message), tb)
         return data
 
     @property
     def capabilities(self):
         if self._capabilities:
             return self._capabilities
 
         self.marionette.start_session()
@@ -762,17 +764,17 @@ class BaseMarionetteTestRunner(object):
                 try:
                     # Establish a socket connection so we can vertify the data come back
                     connection = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                     connection.connect((host, int(port)))
                     connection.close()
                 except Exception as e:
                     exc, val, tb = sys.exc_info()
                     msg = "Connection attempt to {0}:{1} failed with error: {2}"
-                    raise exc, msg.format(host, port, e), tb
+                    raise exc(msg.format(host, port, e), tb)
         if self.workspace:
             kwargs['workspace'] = self.workspace_path
         if self.headless:
             kwargs['headless'] = True
 
         return kwargs
 
     def record_crash(self):
@@ -912,17 +914,17 @@ class BaseMarionetteTestRunner(object):
             # raise only the exception if we were not interrupted
             if not interrupted:
                 raise
         finally:
             self.cleanup()
 
             # reraise previous interruption now
             if interrupted:
-                raise interrupted[0], interrupted[1], interrupted[2]
+                raise(interrupted[0], interrupted[1], interrupted[2])
 
     def _print_summary(self, tests):
         self.logger.info('\nSUMMARY\n-------')
         self.logger.info('passed: {}'.format(self.passed))
         if self.unexpected_successes == 0:
             self.logger.info('failed: {}'.format(self.failed))
         else:
             self.logger.info(

--- a/testing/marionette/harness/marionette_harness/runner/httpd.py
+++ b/testing/marionette/harness/marionette_harness/runner/httpd.py
@@ -3,16 +3,20 @@
 # 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/.
 
 """Specialisation of wptserver.server.WebTestHttpd for testing
 Marionette.
 
 """
+from __future__ import (
+    absolute_import,
+    print_function
+)
 
 import argparse
 import os
 import select
 import sys
 import time
 import urlparse
 

--- a/testing/marionette/harness/marionette_harness/runner/mixins/__init__.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/__init__.py
@@ -1,12 +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
+
 from .browsermob import (
     BrowserMobProxyTestCaseMixin,
     BrowserMobProxyArguments,
     BrowserMobTestCase,
 )
 
 from .window_manager import (
     WindowManagerMixin,

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/__init__.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/__init__.py
@@ -1,6 +1,8 @@
 __version__ = '0.5.0'
 
+from __future__ import absolute_import
+
 from .server import Server
 from .client import Client
 
 __all__ = ['Server', 'Client', 'browsermobproxy']

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/client.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/client.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 import requests
 
 try:
   from urllib.parse import urlencode, unquote
 except ImportError:
   from urllib import urlencode, unquote
 import json
 

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/server.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/server.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 import os
 import platform
 import socket
 import subprocess
 import time
 
 from .client import Client
 

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/webdriver_event_listener.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/browsermobproxy/webdriver_event_listener.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 from selenium.webdriver.support.abstract_event_listener import AbstractEventListener
 
 class WebDriverEventListener(AbstractEventListener):
 
     def __init__(self, client, refs={}):
         self.client = client
         self.hars = []
         self.refs = refs

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/docs/conf.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/docs/conf.py
@@ -6,16 +6,18 @@
 # This file is execfile()d with the current directory set to its containing dir.
 #
 # Note that not all possible configuration values are present in this
 # autogenerated file.
 #
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
+from __future__ import absolute_import
+
 import sys, os
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 sys.path.insert(0, os.path.abspath('../'))
 
 # -- General configuration -----------------------------------------------------

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/setup.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/setup.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 from setuptools import setup, find_packages
 
 setup(name='browsermob-proxy',
       version='0.6.0',
       description='A library for interacting with the Browsermob Proxy',
       author='David Burns',
       author_email='david.burns at theautomatedtester dot co dot uk',
       url='http://oss.theautomatedtester.co.uk/browsermob-proxy-py',

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/test/test_client.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/test/test_client.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 import os.path
 import pytest
 import sys
 
 
 def setup_module(module):
     sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
 

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/test/test_remote.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/test/test_remote.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 from selenium import webdriver
 import selenium.webdriver.common.desired_capabilities
 import os
 import sys
 import time
 import pytest
 
 def setup_module(module):

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/test/test_webdriver.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py/test/test_webdriver.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 from selenium import webdriver
 import selenium.webdriver.common.desired_capabilities
 from selenium.webdriver.common.proxy import Proxy
 import os
 import sys
 import copy
 import time
 import pytest

--- a/testing/marionette/harness/marionette_harness/runner/mixins/browsermob.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/browsermob.py
@@ -1,12 +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
+
 import os
 
 from browsermobproxy import Server
 from marionette_harness import MarionetteTestCase
 
 
 class BrowserMobProxyArguments(object):
     name = 'Browsermob Proxy'

--- a/testing/marionette/harness/marionette_harness/runner/mixins/window_manager.py
+++ b/testing/marionette/harness/marionette_harness/runner/mixins/window_manager.py
@@ -1,12 +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
+
 import sys
 
 from marionette_driver import By, Wait
 
 
 class WindowManagerMixin(object):
 
     _menu_item_new_tab = (By.ID, "menu_newNavigatorTab")
@@ -63,17 +65,17 @@ class WindowManagerMixin(object):
         try:
             if callable(trigger):
                 trigger()
             elif trigger == 'menu':
                 with self.marionette.using_context("chrome"):
                     self.marionette.find_element(*self._menu_item_new_tab).click()
         except Exception:
             exc, val, tb = sys.exc_info()
-            raise exc, 'Failed to trigger opening a new tab: {}'.format(val), tb
+            raise exc('Failed to trigger opening a new tab: {}'.format(val), tb)
         else:
             Wait(self.marionette).until(
                 lambda mn: len(mn.window_handles) == len(current_tabs) + 1,
                 message="No new tab has been opened"
             )
 
             [new_tab] = list(set(self.marionette.window_handles) - set(current_tabs))
 
@@ -94,17 +96,17 @@ class WindowManagerMixin(object):
         try:
             if callable(trigger):
                 trigger()
             else:
                 with self.marionette.using_context("chrome"):
                     self.marionette.execute_script("window.open();")
         except Exception:
             exc, val, tb = sys.exc_info()
-            raise exc, 'Failed to trigger opening a new window: {}'.format(val), tb
+            raise exc('Failed to trigger opening a new window: {}'.format(val), tb)
         else:
             Wait(self.marionette).until(
                 lambda mn: len(mn.chrome_window_handles) == len(current_windows) + 1,
                 message="No new window has been opened"
             )
 
             [new_window] = list(set(self.marionette.chrome_window_handles) - set(current_windows))
 

--- a/testing/marionette/harness/marionette_harness/runner/serve.py
+++ b/testing/marionette/harness/marionette_harness/runner/serve.py
@@ -4,16 +4,21 @@
 # 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/.
 
 """Spawns necessary HTTP servers for testing Marionette in child
 processes.
 
 """
 
+from __future__ import (
+    absolute_import,
+    print_function
+)
+
 import argparse
 import multiprocessing
 import os
 import sys
 
 from collections import defaultdict
 
 import httpd

--- a/testing/marionette/harness/marionette_harness/runtests.py
+++ b/testing/marionette/harness/marionette_harness/runtests.py
@@ -1,12 +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
+
 import sys
 
 import mozlog
 
 from marionette_driver import __version__ as driver_version
 
 from marionette_harness import (
     __version__,

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/conftest.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/conftest.py
@@ -1,12 +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
+
 import pytest
 
 from mock import Mock, MagicMock
 
 from marionette_driver.marionette import Marionette
 
 from marionette_harness.runner.httpd import FixtureServer
 

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/test_httpd.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/test_httpd.py
@@ -1,12 +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
+
 import json
 import os
 import types
 import urllib2
 
 import mozunit
 import pytest
 

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_arguments.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_arguments.py
@@ -1,11 +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
+
 import mozunit
 import pytest
 
 from marionette_harness.runtests import MarionetteArguments
 
 
 @pytest.mark.parametrize("socket_timeout", ['A', '10', '1B-', '1C2', '44.35'])
 def test_parse_arg_socket_timeout(socket_timeout):

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_harness.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_harness.py
@@ -1,12 +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
+
 import mozunit
 import pytest
 
 from mock import Mock, patch, sentinel
 
 import marionette_harness.marionette_test as marionette_test
 
 from marionette_harness.runtests import MarionetteTestRunner, MarionetteHarness, cli

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_runner.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_runner.py
@@ -1,12 +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
+
 import manifestparser
 import mozunit
 import pytest
 
 from mock import Mock, patch, mock_open, sentinel, DEFAULT
 
 from marionette_harness.runtests import MarionetteTestRunner
 

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_test_result.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/test_marionette_test_result.py
@@ -1,12 +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
+
 import mozunit
 import pytest
 
 from marionette_harness import MarionetteTestResult
 
 
 @pytest.fixture
 def empty_marionette_testcase():

--- a/testing/marionette/harness/marionette_harness/tests/harness_unit/test_serve.py
+++ b/testing/marionette/harness/marionette_harness/tests/harness_unit/test_serve.py
@@ -1,12 +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
+
 import types
 
 import mozunit
 import pytest
 
 from marionette_harness.runner import serve
 from marionette_harness.runner.serve import iter_proc, iter_url
 

--- a/testing/marionette/harness/marionette_harness/tests/unit/single_finger_functions.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/single_finger_functions.py
@@ -1,8 +1,10 @@
+from __future__ import absolute_import
+
 from marionette_driver.marionette import Actions
 from marionette_driver.errors import TimeoutException
 from marionette_driver.by import By
 
 
 def wait_for_condition_else_raise(marionette, wait_for_condition, expected, script):
     try:
         wait_for_condition(lambda m: expected in m.execute_script(script))

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_accessibility.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_accessibility.py
@@ -1,12 +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
+
 import sys
 import unittest
 
 from marionette_driver.by import By
 from marionette_driver.errors import (
     ElementNotAccessibleException,
     ElementNotInteractableException,
     ElementClickInterceptedException,

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_addons.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_addons.py
@@ -1,12 +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
+
 import os
 
 from marionette_driver.addons import Addons, AddonInstallException
 from marionette_harness import MarionetteTestCase
 
 
 here = os.path.abspath(os.path.dirname(__file__))
 

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_anonymous_content.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_anonymous_content.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 from marionette_driver.errors import NoSuchElementException
 from marionette_driver.marionette import HTMLElement
 
 from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class TestAnonymousNodes(WindowManagerMixin, MarionetteTestCase):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_browsermobproxy.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_browsermobproxy.py
@@ -1,10 +1,12 @@
 import datetime
 
+from __future__ import absolute_import
+
 from marionette_harness.runner import BrowserMobTestCase
 
 
 class TestBrowserMobProxy(BrowserMobTestCase):
     """To run this test, you'll need to download the browsermob-proxy from
        http://bmp.lightbody.net/, and then pass the path to the startup
        script (typically /path/to/browsermob-proxy-2.0.0/bin/browsermob-proxy)
        as the --browsermob-script argument when running runtests.py.

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_capabilities.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_capabilities.py
@@ -1,12 +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/.
 
+from __future__ import (
+    absolute_import, 
+    print_function
+)
+
 from marionette_driver.errors import SessionNotCreatedException
 
 from marionette_harness import MarionetteTestCase
 
 # Unlike python 3, python 2 doesn't have a proper implementation of realpath or
 # samefile for Windows. However this function, which does exactly what we want,
 # was added to python 2 to fix an issue with tcl installations and symlinks.
 from FixTk import convert_path

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 
 from marionette_harness import MarionetteTestCase
 
 
 class TestCheckbox(MarionetteTestCase):
     def test_selected(self):
         test_html = self.marionette.absolute_url("test.html")

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox_chrome.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 
 from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class TestSelectedChrome(WindowManagerMixin, MarionetteTestCase):
 
     def setUp(self):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_chrome.py
@@ -8,16 +8,18 @@
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 #Unless required by applicable law or agreed to in writing, software
 #distributed under the License is distributed on an "AS IS" BASIS,
 #WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #See the License for the specific language governing permissions and
 #limitations under the License.
 
+from __future__ import absolute_import
+
 from marionette_driver import By
 
 from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class ChromeTests(WindowManagerMixin, MarionetteTestCase):
 
     def setUp(self):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_chrome_element_css.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_chrome_element_css.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 
 from marionette_harness import MarionetteTestCase
 
 
 class TestChromeElementCSS(MarionetteTestCase):
 
     def get_element_computed_style(self, element, property):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_clearing.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_clearing.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 from marionette_driver.errors import InvalidElementStateException
 
 from marionette_harness import MarionetteTestCase
 
 
 class TestClear(MarionetteTestCase):
     def testWriteableTextInputShouldClear(self):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_cli_arguments.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_cli_arguments.py
@@ -1,12 +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
+
 import copy
 
 from marionette_harness import MarionetteTestCase
 
 
 class TestCommandLineArguments(MarionetteTestCase):
 
     def setUp(self):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_click.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_click.py
@@ -1,12 +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
+
 import urllib
 
 from marionette_driver import By, errors
 
 from marionette_harness import (
     MarionetteTestCase,
     run_if_e10s,
     skip_if_mobile,

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_click_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_click_chrome.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 
 from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class TestClickChrome(WindowManagerMixin, MarionetteTestCase):
 
     def setUp(self):

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_click_scrolling.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_click_scrolling.py
@@ -1,12 +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
+
 from marionette_driver.by import By
 from marionette_driver.errors import MoveTargetOutOfBoundsException
 
 from marionette_harness import MarionetteTestCase, skip, skip_if_mobile
 
 
 class TestClickScrolling(MarionetteTestCase):
 

--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/api/software_update.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/api/software_update.py
@@ -363,18 +363,18 @@ class SoftwareUpdate(BaseLib):
         :param update_url: URL to the update snippet
         """
         import urllib2
         try:
             response = urllib2.urlopen(update_url)
             return response.read()
         except urllib2.URLError:
             exc, val, tb = sys.exc_info()
-            raise Exception, "Failed to retrieve update snippet '{}': {}".format(
-                update_url, val), tb
+            raise Exception("Failed to retrieve update snippet '{}': {}".format(
+                update_url, val), tb)
 
     def get_formatted_update_url(self, force=False):
         """Retrieve the formatted AUS update URL the update snippet is retrieved from.
 
         :param force: Boolean flag to force an update check
 
         :returns: The URL of the update snippet
         """