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

Tools/Scripts/webkitpy/layout_tests/port/mock_drt_unittest.py

 # Copyright (C) 2011 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.
 
 """Unit tests for MockDRT."""
 
 import sys
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.common import newstringio
 from webkitpy.common.system.systemhost_mock import MockSystemHost
 from webkitpy.layout_tests.port import mock_drt
 from webkitpy.layout_tests.port import port_testcase
 from webkitpy.layout_tests.port import test
 from webkitpy.layout_tests.port.factory import PortFactory
 from webkitpy.tool import mocktool
 
 
@@ skipping 149 matching lines @@
         self.assertTest('passes/audio.html', pixel_tests=True,
                         drt_output=['Content-Type: audio/wav\n',
                          'Content-Transfer-Encoding: base64\n',
                          'YXVkaW8td2F2',
                          '\n',
                          '#EOF\n',
                          '#EOF\n'])
 
     def test_virtual(self):
         self.assertTest('virtual/passes/text.html', True)