style(endpoints/api/suconfig_models_interface.py): formatted file

### Description of Changes

Issue: https://coreosdev.atlassian.net/browse/QUAY-750

## Reviewer Checklist

- [ ] It works!
- [ ] Comments provide sufficient explanations for the next contributor
- [ ] Tests cover changes and corner cases
- [ ] Follows Quay syntax patterns and format

endpoints/api/suconfig_models_interface.py

@@ -1,11 +1,13 @@
 from abc import ABCMeta, abstractmethod
 from six import add_metaclass
 
+
 @add_metaclass(ABCMeta)
 class SuperuserConfigDataInterface(object):
   """
   Interface that represents all data store interactions required by the superuser config API.
   """
+
   @abstractmethod
   def is_valid(self):
     """