Remove debugging short circuit

Circumventing this exception was only added for debugging purposes.

app/models/__init__.py

@@ -15,7 +15,6 @@ class JSONModel():
     def __getattr__(self, attr):
         if attr in self.ALLOWED_PROPERTIES:
             return self._dict[attr]
-        return
         raise AttributeError('`{}` is not a {} attribute'.format(
             attr,
             self.__class__.__name__.lower(),