Remove url element from parent class to avoid annoying errors

common/lib/xmodule/xmodule/grading_service_module.py

@@ -22,7 +22,6 @@ class GradingService(object):
     def __init__(self, config):
         self.username = config['username']
         self.password = config['password']
-        self.url = config['url']
         self.session = requests.session()
         self.system = config['system']