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

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

 # Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)
 #
 # 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 tests for common.py."""
 
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from common import CarriageReturnChecker
 from common import TabChecker
 
 # FIXME: The unit tests for the cpp, text, and common checkers should
 #        share supporting test code. This can include, for example, the
 #        mock style error handling code and the code to check that all
 #        of a checker's categories are covered by the unit tests.
 #        Such shared code can be located in a shared test file, perhaps
 #        even this file.
@@ skipping 76 matching lines @@
         checker.check(input_lines)
         self.assertEqual(self._error_lines, error_lines)
 
     def test_notab(self):
         self.assert_tab([''], [])
         self.assert_tab(['foo', 'bar'], [])
 
     def test_tab(self):
         self.assert_tab(['\tfoo'], [1])
         self.assert_tab(['line1', '\tline2', 'line3\t'], [2, 3])