BOM-1121

-Updated middleware setting to use use middleware insted of
middleware_classes
-github install of django-method-override fork to support
new style middleware in django1.11

openedx/core/djangoapps/safe_sessions/testing.py

@@ -20,7 +20,7 @@ def safe_cookie_test_session_patch():
         used, by checking the middleware settings.
         """
         return (
-            'openedx.core.djangoapps.safe_sessions.middleware.SafeSessionMiddleware' in settings.MIDDLEWARE_CLASSES
+            'openedx.core.djangoapps.safe_sessions.middleware.SafeSessionMiddleware' in settings.MIDDLEWARE
         )
 
     ## session_id --> safe_cookie_data ##