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

Tools/Scripts/webkitpy/layout_tests/run_webkit_tests_unittest.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 # Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
 # Copyright (C) 2011 Apple 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:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 10 matching lines @@
 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 # OWNER OR 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 ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (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 Queue
+import StringIO
 import codecs
 import json
 import logging
 import os
 import platform
-import Queue
 import re
-import StringIO
 import sys
 import thread
 import time
 import threading
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.system import outputcapture, path
 from webkitpy.common.system.crashlogs_unittest import make_mock_crash_report_darwin
 from webkitpy.common.system.systemhost import SystemHost
 from webkitpy.common.host import Host
 from webkitpy.common.host_mock import MockHost
 
 from webkitpy.layout_tests import port
 from webkitpy.layout_tests import run_webkit_tests
 from webkitpy.layout_tests.models import test_run_results
@@ skipping 998 matching lines @@
         stderr = StringIO.StringIO()
         res = run_webkit_tests.main(['--platform', 'test', '--exit-after-n-failures', '1',
                                      'failures/unexpected/missing_text.html',
                                      'failures/unexpected/missing_image.html'],
                                     stdout, stderr)
         self.assertEqual(res, test_run_results.EARLY_EXIT_STATUS)
         self.assertEqual(stdout.getvalue(),
                 ('\n'
                  'Regressions: Unexpected missing results (1)\n'
                  '  failures/unexpected/missing_image.html [ Missing ]\n\n'))