Merge release 21.9.2 (#2313)

sanic/app.py

@@ -1631,7 +1631,9 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
         self._future_registry.clear()
         self.signalize()
         self.finalize()
-        ErrorHandler.finalize(self.error_handler)
+        ErrorHandler.finalize(
+            self.error_handler, fallback=self.config.FALLBACK_ERROR_FORMAT
+        )
         TouchUp.run(self)
 
     async def _server_event(

sanic/handlers.py

@@ -38,7 +38,14 @@ class ErrorHandler:
         self.base = base
 
     @classmethod
-    def finalize(cls, error_handler):
+    def finalize(cls, error_handler, fallback: Optional[str] = None):
+        if (
+            fallback
+            and fallback != "auto"
+            and error_handler.fallback == "auto"
+        ):
+            error_handler.fallback = fallback
+
         if not isinstance(error_handler, cls):
             error_logger.warning(
                 f"Error handler is non-conforming: {type(error_handler)}"