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

Tools/Scripts/webkitpy/style/checkers/jsonchecker_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 jsonchecker.py."""
 
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 import jsonchecker
 
 
 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):
@@ skipping 66 matching lines @@
                       "slavenames": ["apple-xserve-4"]
                     }
                    ],
 
     "schedulers": [ { "type": "PlatformSpecificScheduler", "platform": "mac-snowleopard", "branch": "trunk", "treeStableTimer": 45.0,
                       "builderNames": ["SnowLeopard Intel Release (Build)", "SnowLeopard Intel Debug (Build)"]
                     }
                   ]
 }
 """)