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

Tools/Scripts/webkitpy/tool/servers/rebaselineserver_unittest.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
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 import json
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.net import layouttestresults_unittest
 from webkitpy.common.host_mock import MockHost
 from webkitpy.layout_tests.layout_package.json_results_generator import strip_json_wrapper
 from webkitpy.layout_tests.port.base import Port
 from webkitpy.tool.commands.rebaselineserver import TestConfig, RebaselineServer
 from webkitpy.tool.servers import rebaselineserver
 
 
 class RebaselineTestTest(unittest.TestCase):
@@ skipping 263 matching lines @@
         port_name = "mac"
         FALLBACK_PATHS = {'': ['mac']}
 
     return TestConfig(
         TestMacPort(host, 'mac'),
         layout_tests_directory,
         results_directory,
         ('mac', 'mac-leopard', 'win', 'linux'),
         host.filesystem,
         host.scm())