Symlink test_env.py instead of test_support in preparation of jinja2.

appengine/components/components/datastore_utils/mapping_test.py

 #!/usr/bin/env python
 # Copyright 2014 The Swarming Authors. All rights reserved.
 # Use of this source code is governed by the Apache v2.0 license that can be
 # found in the LICENSE file.
 
 import sys
 import unittest
 
-from test_support import test_env
+import test_env
 test_env.setup_test_env()
 
 from google.appengine.ext import ndb
 
 from components.datastore_utils import mapping
 from test_support import test_case
 
 
 class EntityX(ndb.Model):
   a = ndb.IntegerProperty()
@@ skipping 100 matching lines @@
         [EntityX(id=i, a=2) for i in xrange(2, 42, 4)] * 2,
         key=lambda x: (x.key.id, x.to_dict()))
     actual.sort(key=lambda x: (x.key.id, x.to_dict()))
     self.assertEqual(expected, actual)
 
 
 if __name__ == '__main__':
   if '-v' in sys.argv:
     unittest.TestCase.maxDiff = None
   unittest.main()