Create a new depot_tools_testing_lib to move utility modules there

tests/trychange_unittest.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 trychange.py."""
 
 import os
 import sys
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-from super_mox import SuperMoxTestBase
+from testing_support.super_mox import SuperMoxTestBase
 
 import subprocess2
 import trychange
 
 
 class TryChangeTestsBase(SuperMoxTestBase):
   """Setups and tear downs the mocks but doesn't test anything as-is."""
   def setUp(self):
     SuperMoxTestBase.setUp(self)
     self.mox.StubOutWithMock(subprocess2, 'communicate')
@@ skipping 82 matching lines @@
     self.mox.ReplayAll()
     git = trychange.GIT(self.options, self.fake_root, self.options.files)
     self.assertEqual(git.GetFileNames(), self.expected_files)
     self.assertEqual(git.checkout_root, self.fake_root)
     self.assertEqual(git.GenerateDiff(), 'A diff')
 
 
 if __name__ == '__main__':
   import unittest
   unittest.main()