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

Tools/Scripts/webkitpy/style/checkers/xml_unittest.py

 # Copyright (C) 2010 Apple 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:
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
 #     documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS 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 APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR
 # ANY DIRECT, INDIRECT, INCIDENTAL, 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 test for xml.py."""
 
-import webkitpy.thirdparty.unittest2 as unittest
-
+import unittest
 import xml
 
 
 class MockErrorHandler(object):
     def __init__(self, handle_style_error):
         self.turned_off_filtering = False
         self._handle_style_error = handle_style_error
 
     def turn_off_line_filtering(self):
         self.turned_off_filtering = True
@@ skipping 41 matching lines @@
     def test_init(self):
         error_handler = MockErrorHandler(self.mock_handle_style_error)
         checker = xml.XMLChecker('foo.xml', error_handler)
         self.assertEqual(checker._handle_style_error, error_handler)
 
     def test_missing_closing_tag(self):
         self.assert_error(3, 'xml/syntax', '<foo>\n<bar>\n</foo>\n')
 
     def test_no_error(self):
         self.assert_no_error('<foo>\n</foo>')