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

Tools/Scripts/webkitpy/common/system/filesystem_mock_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 10 matching lines @@
 # OWNER OR 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.
 
 import os
 import re
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 
 from webkitpy.common.system import filesystem_mock
 from webkitpy.common.system import filesystem_unittest
 
 
 class MockFileSystemTest(unittest.TestCase, filesystem_unittest.GenericFileSystemTests):
     def setUp(self):
         self.fs = filesystem_mock.MockFileSystem()
         self.setup_generic_test_dir()
@@ skipping 36 matching lines @@
                          'foo/',
                          'foo/.',
                          'foo/bar',
                          '/foo',
                          'foo/../bar',
                          'foo/../bar/baz',
                          '../foo')
 
     def test_relpath_win32(self):
         pass