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

Tools/Scripts/webkitpy/common/thread/threadedmessagequeue_unittest.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
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 # 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
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 # in the documentation and/or other materials provided with the
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 # contributors may be used to endorse or promote products derived from
 # this software without specific prior written permission.
 #
 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common.thread.threadedmessagequeue import ThreadedMessageQueue
 
 class ThreadedMessageQueueTest(unittest.TestCase):
 
     def test_basic(self):
         queue = ThreadedMessageQueue()
         queue.post("Hello")
         queue.post("There")
         (messages, is_running) = queue.take_all()
         self.assertEqual(messages, ["Hello", "There"])
         self.assertTrue(is_running)
         (messages, is_running) = queue.take_all()
         self.assertEqual(messages, [])
         self.assertTrue(is_running)
         queue.post("More")
         queue.stop()
         queue.post("Messages")
         (messages, is_running) = queue.take_all()
         self.assertEqual(messages, ["More", "Messages"])
         self.assertFalse(is_running)
         (messages, is_running) = queue.take_all()
         self.assertEqual(messages, [])
         self.assertFalse(is_running)