run black over stubs, add checking to travis

django-stubs-generated/utils/module_loading.pyi

@@ -1,6 +1,5 @@
 from typing import Any, Optional
 
-
 def import_string(dotted_path: str) -> Any: ...
 def autodiscover_modules(*args: Any, **kwargs: Any) -> None: ...
 def module_has_submodule(package: Any, module_name: str) -> bool: ...