message: Fix an unused variable warning with python parameterless callbacks
diff: @@ -866,6 +866,10 @@ struct varfunc
  currentarg = 0;
  + // avoid unused parameter errors when calling a parameter-less function
  + (void)self;
  + (void)funcname;
  +
  using expand_type = int[];
  (void)expand_type{0, (push_arg(self, funcname, params), 0)...};
  }
  