lint issues

Author: Akol125

mns_subscription/src/mns_service.py

@@ -47,5 +47,5 @@ def subscribe_notification(self) -> dict | None:
         elif response.status_code == 404:
             return None
         else:
-            msg = f"MNS subscription failed"
+            msg = "MNS subscription failed"
             raise UnhandledResponseError(response=response.json(), message=msg)