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

Tools/Scripts/webkitpy/layout_tests/controllers/repaint_overlay_unittest.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import optparse
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from webkitpy.layout_tests.controllers import repaint_overlay
 
 
 LAYER_TREE = """{
   "bounds":[800.00,600.00],
   "children":[
     {
       "position": [8.00, 80.00],
       "bounds": [800.00, 600.00],
       "contentsOpaque": true,
       "drawsContent": true,
       "repaintRects": [
         [8, 108, 100, 100],
         [0, 216, 800, 100]
       ]
     }
   ]
 }
 """
 
 class TestRepaintOverlay(unittest.TestCase):
     def test_result_contains_repaint_rects(self):
         self.assertTrue(repaint_overlay.result_contains_repaint_rects(LAYER_TREE))
         self.assertFalse(repaint_overlay.result_contains_repaint_rects('ABCD'))
 
     def test_extract_layer_tree(self):
         self.assertEquals(LAYER_TREE, repaint_overlay.extract_layer_tree(LAYER_TREE))