combine base_unittest.py modules from gm and tools

gm/rebaseline_server/imagepair_test.py

Index: gm/rebaseline_server/imagepair_test.py
diff --git a/gm/rebaseline_server/imagepair_test.py b/gm/rebaseline_server/imagepair_test.py
index 14fe4c1143dbab8437ffc637f50609a4e8b8d307..ef7695acacc80af6e9873cb4e3ea8aba42de36ba 100755
--- a/gm/rebaseline_server/imagepair_test.py
+++ b/gm/rebaseline_server/imagepair_test.py
@@ -26,11 +26,11 @@ IMG_URL_BASE = ('http://chromium-skia-gm.commondatastorage.googleapis.com/'
 class ImagePairTest(unittest.TestCase):
 
   def setUp(self):
-    self._temp_dir = tempfile.mkdtemp()
+    self.temp_dir = tempfile.mkdtemp()
     self.maxDiff = None
 
   def tearDown(self):
-    shutil.rmtree(self._temp_dir)
+    shutil.rmtree(self.temp_dir)
 
   def shortDescription(self):
     """Tells unittest framework to not print docstrings for test cases."""
@@ -163,7 +163,7 @@ class ImagePairTest(unittest.TestCase):
         ],
     ]
 
-    db = imagediffdb.ImageDiffDB(self._temp_dir)
+    db = imagediffdb.ImageDiffDB(self.temp_dir)
     for selftest in selftests:
       image_pair = imagepair.ImagePair(
           image_diff_db=db,