Create a new depot_tools_testing_lib to move utility modules there

PRESUBMIT.py

 # 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.
 
 """Top-level presubmit script for depot tools.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into depot_tools.
 """
 
@@ skipping 11 matching lines @@
         'Otherwise, you break depot_tools on python 2.5, you get to keep the '
         'pieces.'))
 
 
   results.extend(input_api.canned_checks.CheckOwners(input_api, output_api))
   black_list = list(input_api.DEFAULT_BLACK_LIST) + [
       r'^cpplint\.py$',
       r'^cpplint_chromium\.py$',
       r'^python_bin[\/\\].+',
       r'^svn_bin[\/\\].+',
-      r'^tests[\/\\]\w+?[\/\\].+']
+      r'^testing_support[\/\\]_rietveld[\/\\].+']
   results.extend(input_api.canned_checks.RunPylint(
       input_api,
       output_api,
       white_list=[r'.*\.py$'],
       black_list=black_list))
 
   # TODO(maruel): Make sure at least one file is modified first.
   # TODO(maruel): If only tests are modified, only run them.
   results.extend(input_api.canned_checks.RunUnitTestsInDirectory(
       input_api,
       output_api,
       'tests',
       whitelist=[r'.*test\.py$'],
       blacklist=tests_to_black_list))
   return results
 
 
 def RunGitClTests(input_api, output_api):
   """Run all the shells scripts in the directory test.
   """
   if input_api.platform == 'win32':
     # Skip for now as long as the test scripts are bash scripts.
     return []
 
   # First loads a local Rietveld instance.
   import sys
   old_sys_path = sys.path
   try:
     sys.path = [input_api.PresubmitLocalPath()] + sys.path
-    from tests import local_rietveld  # pylint: disable=W0403
+    from testing_support import local_rietveld
     server = local_rietveld.LocalRietveld()
   finally:
     sys.path = old_sys_path
 
   results = []
   try:
     # Start a local rietveld instance to test against.
     server.start_server()
     test_path = input_api.os_path.abspath(
         input_api.os_path.join(input_api.PresubmitLocalPath(), 'tests'))
@@ skipping 34 matching lines @@
 
 
 def CheckChangeOnCommit(input_api, output_api):
   output = []
   output.extend(CommonChecks(input_api, output_api, []))
   output.extend(input_api.canned_checks.CheckDoNotSubmit(
       input_api,
       output_api))
   output.extend(RunGitClTests(input_api, output_api))
   return output