Added check_apps_ready() to Apps.get_containing_app_config()

django/apps/registry.py

@@ -227,9 +227,7 @@ class Apps(object):
         Returns the app config for the inner application in case of nesting.
         Returns None if the object isn't in any registered app config.
         """
-        # In Django 1.7 and 1.8, it's allowed to call this method at import
-        # time, even while the registry is being populated. In Django 1.9 and
-        # later, that should be forbidden with `self.check_apps_ready()`.
+        self.check_apps_ready()
         candidates = []
         for app_config in self.app_configs.values():
             if object_name.startswith(app_config.name):