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

Tools/Scripts/webkitpy/performance_tests/perftest_unittest.py

 # Copyright (C) 2013 Google 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.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 11 matching lines @@
 # 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 StringIO
 import json
 import math
-import unittest2 as unittest
+import unittest
 
 from webkitpy.common.host_mock import MockHost
 from webkitpy.common.system.outputcapture import OutputCapture
 from webkitpy.layout_tests.port.driver import DriverOutput
 from webkitpy.layout_tests.port.test import TestDriver
 from webkitpy.layout_tests.port.test import TestPort
 from webkitpy.performance_tests.perftest import ChromiumStylePerfTest
 from webkitpy.performance_tests.perftest import PerfTest
 from webkitpy.performance_tests.perftest import PerfTestMetric
 from webkitpy.performance_tests.perftest import PerfTestFactory
@@ skipping 189 matching lines @@
 
 
 class TestPerfTestFactory(unittest.TestCase):
     def test_regular_test(self):
         test = PerfTestFactory.create_perf_test(MockPort(), 'some-dir/some-test', '/path/some-dir/some-test')
         self.assertEqual(test.__class__, PerfTest)
 
     def test_inspector_test(self):
         test = PerfTestFactory.create_perf_test(MockPort(), 'inspector/some-test', '/path/inspector/some-test')
         self.assertEqual(test.__class__, ChromiumStylePerfTest)