Remove tools usage of //third_party/pymock

Removes usage of //third_party/pymock from //tools in favor of the
version provided by vpython. This is so that //third_party/pymock can
eventually be removed.

Bug: 1094489
Change-Id: I0d4b6484c9c44b93fb76613a3e194c3da811550d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2255136Reviewed-by: Roberto Carrillo <robertocn@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781422}

tools/checkteamtags/checkteamtags_test.py

@@ -9,9 +9,6 @@ import unittest
 
 import checkteamtags
 
-SRC = os.path.join(os.path.dirname(__file__), os.path.pardir, os.path.pardir)
-sys.path.append(os.path.join(SRC, 'third_party', 'pymock'))
-
 import mock
 
 

tools/checkteamtags/extract_components_test.py

@@ -12,9 +12,6 @@ from StringIO import StringIO
 
 import extract_components
 
-SRC = os.path.join(os.path.dirname(__file__), os.path.pardir, os.path.pardir)
-sys.path.append(os.path.join(SRC, 'third_party', 'pymock'))
-
 import mock
 
 

tools/checkteamtags/owners_file_tags_test.py

@@ -10,9 +10,6 @@ import unittest
 
 import owners_file_tags
 
-SRC = os.path.join(os.path.dirname(__file__), os.path.pardir, os.path.pardir)
-sys.path.append(os.path.join(SRC, 'third_party', 'pymock'))
-
 import mock
 
 @contextmanager

tools/checkteamtags/run_tests

-#!/usr/bin/env python
+#!/usr/bin/env vpython
 # Copyright 2017 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
@@ -12,8 +12,6 @@ import sys
 import unittest
 import logging
 
-SRC = os.path.join(os.path.dirname(__file__), os.path.pardir, os.path.pardir)
-
 
 def main():
   if 'full-log' in sys.argv: