Revert of Remove unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/scm_unittest.py

 # Copyright (C) 2009 Google Inc. All rights reserved.
 # Copyright (C) 2009 Apple Inc. All rights reserved.
 # Copyright (C) 2011 Daniel Bates (dbates@intudata.com). All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #    * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 10 matching lines @@
 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+import atexit
+import os
+import shutil
 import unittest
 
 from webkitpy.common.system.executive import Executive, ScriptError
 from webkitpy.common.system.executive_mock import MockExecutive
 from webkitpy.common.system.filesystem import FileSystem
 from webkitpy.common.system.filesystem_mock import MockFileSystem
 from webkitpy.common.checkout.scm.detection import detect_scm_system
-from webkitpy.common.checkout.scm.git import Git
+from webkitpy.common.checkout.scm.git import Git, AmbiguousCommitError
+from webkitpy.common.checkout.scm.scm import SCM
 
 
 class SCMTestBase(unittest.TestCase):
     def __init__(self, *args, **kwargs):
         super(SCMTestBase, self).__init__(*args, **kwargs)
         self.scm = None
         self.executive = None
         self.fs = None
         self.original_cwd = None
 
@@ skipping 181 matching lines @@
         scm = self.make_scm()
         scm.find_checkout_root = lambda path: ''
         scm._run_git = lambda args: 'Date: 2013-02-08 08:05:49 +0000'
         self.assertEqual(scm.timestamp_of_revision('some-path', '12345'), '2013-02-08T08:05:49Z')
 
         scm._run_git = lambda args: 'Date: 2013-02-08 01:02:03 +0130'
         self.assertEqual(scm.timestamp_of_revision('some-path', '12345'), '2013-02-07T23:32:03Z')
 
         scm._run_git = lambda args: 'Date: 2013-02-08 01:55:21 -0800'
         self.assertEqual(scm.timestamp_of_revision('some-path', '12345'), '2013-02-08T09:55:21Z')