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

Tools/Scripts/webkitpy/common/system/outputcapture.py

 # Copyright (c) 2009, 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 12 matching lines @@
 # 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.
 #
 # Class for unittest support.  Used for capturing stderr/stdout.
 
 import logging
 import sys
+import unittest
+
 from StringIO import StringIO
 
-import webkitpy.thirdparty.unittest2 as unittest
-
 
 class OutputCapture(object):
     # By default we capture the output to a stream. Other modules may override
     # this function in order to do things like pass through the output. See
     # webkitpy.test.main for an example.
     @staticmethod
     def stream_wrapper(stream):
         return StringIO()
 
     def __init__(self):
@@ skipping 73 matching lines @@
         del self.__captured_stdout
         del self.__captured_stderr
         self.output_capture.restore_output()
         unittest.TestCase.tearDown(self)
 
     def assertStdout(self, expected_stdout):
         self.assertEqual(expected_stdout, self.__captured_stdout.getvalue())
 
     def assertStderr(self, expected_stderr):
         self.assertEqual(expected_stderr, self.__captured_stderr.getvalue())