Remove thirdparty/unittest2 from webkitpy and require python2.7.

Tools/Scripts/webkitpy/common/system/crashlogs_unittest.py

 # Copyright (C) 2011 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 #
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
 #     documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 # DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS 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
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 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.system.crashlogs import CrashLogs
 from webkitpy.common.system.filesystem_mock import MockFileSystem
 from webkitpy.common.system.systemhost import SystemHost
 from webkitpy.common.system.systemhost_mock import MockSystemHost
 from webkitpy.thirdparty.mock import Mock
 
 
 def make_mock_crash_report_darwin(process_name, pid):
     return """Process:         {process_name} [{pid}]
@@ skipping 71 matching lines @@
 
         filesystem.read_text_file = bad_read
         log = crash_logs.find_newest_log("DumpRenderTree", 28531, include_errors=True)
         self.assertIn('IOError: No such file or directory', log)
 
         filesystem = MockFileSystem(files)
         crash_logs = CrashLogs(MockSystemHost(filesystem=filesystem))
         filesystem.mtime = bad_mtime
         log = crash_logs.find_newest_log("DumpRenderTree", newer_than=1.0, include_errors=True)
         self.assertIn('OSError: No such file or directory', log)