Create a new depot_tools_testing_lib to move utility modules there

tests/checkout_test.py

 #!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Unit tests for checkout.py."""
 
 from __future__ import with_statement
 import logging
 import os
 import shutil
 import sys
 import unittest
 from xml.etree import ElementTree
 
 ROOT_DIR = os.path.dirname(os.path.abspath(__file__))
 sys.path.insert(0, os.path.dirname(ROOT_DIR))
 
+from testing_support import fake_repos
+from testing_support.patches_data import GIT, RAW
+
 import checkout
 import patch
 import subprocess2
-from tests import fake_repos
-from tests.patches_data import GIT, RAW
 
 
 # pass -v to enable it.
 DEBUGGING = False
 
 # A patch that will fail to apply.
 BAD_PATCH = ''.join(
     [l for l in GIT.PATCH.splitlines(True) if l.strip() != 'e'])
 
 
@@ skipping 543 matching lines @@
   if '-v' in sys.argv:
     DEBUGGING = True
     logging.basicConfig(
         level=logging.DEBUG,
         format='%(levelname)5s %(filename)15s(%(lineno)3d): %(message)s')
   else:
     logging.basicConfig(
         level=logging.ERROR,
         format='%(levelname)5s %(filename)15s(%(lineno)3d): %(message)s')
   unittest.main()