fix skip message.

Author: rouilj

test/test_memorydb.py

@@ -66,7 +66,7 @@ def setUp(self):
 
     # doesn't work for memory as it uses a mock for session db.
     def testUpdateTimestamp(self):
-        self.skipTest("This test does is not implemented for memorydb.")        
+        self.skipTest("This test is not implemented for memorydb.")        
 
 # vim: set filetype=python ts=4 sw=4 et si