Fix pylint warnings in webkitpy/common/.

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 17 matching lines @@
 # (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 unittest
 
 from webkitpy.common.system.executive import Executive, ScriptError
 from webkitpy.common.system.executive_mock import MockExecutive, MockExecutive2
 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 AmbiguousCommitError
 from webkitpy.common.checkout.scm.git import Git
-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 204 matching lines @@
         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')
 
     def test_get_issue_number(self):
         scm = Git(cwd='.', executive=MockExecutive2(output='Issue number: 12345 (http://crrev.com/12345)'))
         issue_number = scm.get_issue_number()
         self.assertEqual(issue_number, '12345')
         scm2 = Git(cwd='.', executive=MockExecutive2(output='Issue number: None (None)'))
         issue_number = scm2.get_issue_number()
         self.assertEqual(issue_number, 'None')