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

Tools/Scripts/webkitpy/common/net/buildbot/buildbot_unittest.py

 # Copyright (C) 2009 Google Inc. All rights reserved.
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-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.net.layouttestresults import LayoutTestResults
 from webkitpy.common.net.buildbot import BuildBot, Builder, Build
 from webkitpy.layout_tests.models import test_results
 from webkitpy.layout_tests.models import test_failures
 from webkitpy.thirdparty.BeautifulSoup import BeautifulSoup
 
 
 class BuilderTest(unittest.TestCase):
     def _mock_test_result(self, testname):
@@ skipping 363 matching lines @@
         b._fetch_revision_to_build_map = self._fetch_revision_to_build_map
         self.assertEqual("correct build", b.latest_cached_build())
 
     def results_url(self):
         return "some-url"
 
     def test_results_zip_url(self):
         b = Build(None, 123, 123, False)
         b.results_url = self.results_url
         self.assertEqual("some-url.zip", b.results_zip_url())