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

Tools/Scripts/webkitpy/layout_tests/port/browser_test_unittest.py

 # Copyright (C) 2014 Google Inc. All rights reserved.
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-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.system.executive_mock import MockExecutive2
 from webkitpy.common.system.systemhost_mock import MockSystemHost
 from webkitpy.tool.mocktool import MockOptions
 
 from webkitpy.layout_tests.models import test_run_results
 from webkitpy.layout_tests.port import browser_test
 from webkitpy.layout_tests.port import port_testcase
 from webkitpy.layout_tests.port import browser_test_driver
 
@@ skipping 66 matching lines @@
         self.assertFalse('.app/Contents/MacOS' in test_port._path_to_driver())
 
     def test_check_sys_deps(self):
         port = self.make_port()
         port._executive = MockExecutive2(exit_code=0)
         self.assertEqual(port.check_sys_deps(needs_http=False), test_run_results.OK_EXIT_STATUS)
 
     def test_default_timeout_ms(self):
         self.assertEqual(self.make_port(options=MockOptions(configuration='Release')).default_timeout_ms(), 20000)
         self.assertEqual(self.make_port(options=MockOptions(configuration='Debug')).default_timeout_ms(), 60000)