run black over stubs, add checking to travis

django-stubs-generated/utils/xmlutils.pyi

@@ -1,15 +1,9 @@
 from typing import Any, Dict, Optional
 from xml.sax.saxutils import XMLGenerator
 
-
 class UnserializableContentError(ValueError): ...
 
 class SimplerXMLGenerator(XMLGenerator):
-    def addQuickElement(
-        self,
-        name: str,
-        contents: Optional[str] = ...,
-        attrs: Optional[Dict[str, str]] = ...,
-    ) -> None: ...
+    def addQuickElement(self, name: str, contents: Optional[str] = ..., attrs: Optional[Dict[str, str]] = ...) -> None: ...
     def characters(self, content: str) -> None: ...
     def startElement(self, name: str, attrs: Dict[str, str]) -> None: ...