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

Tools/Scripts/webkitpy/layout_tests/print_layout_test_times_unittest.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
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-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.host_mock import MockHost
 from webkitpy.layout_tests.print_layout_test_times import main
 
 
 class PrintLayoutTestTimesTest(unittest.TestCase):
 
     def check(self, args, expected_output, files=None):
         host = MockHost()
         fs = host.filesystem
@@ skipping 60 matching lines @@
     def test_backward_one(self):
         self.check(['-b', '1'],
                    "bar/bar1 100\n"
                    "foo/foo1 100\n"
                    "foo/foo2 100\n")
 
     def test_path_to_file(self):
         # Tests that we can use a custom file rather than the port's default.
         self.check(['/tmp/times_ms.json'], "foo/bar.html 1\n",
                    files={'/tmp/times_ms.json': '{"foo":{"bar.html": 1}}'})