method returns a boolean

xpra/notifications/dbus_notifier.py

@@ -167,7 +167,7 @@ def ActionInvoked(self, actual_id : int, action) -> None:
 
     def NotifyError(self, dbus_error, *_args) -> bool:
         if not self.dbusnotify:
-            return
+            return False
         try:
             if isinstance(dbus_error, dbus.exceptions.DBusException):
                 message = dbus_error.get_dbus_message()