message: Fix do_on_error
diff: @@ -199,7 +199,7 @@ struct do_on_error_step {
  template <class Next, class... Steps>
  void on_error(const error& what, Next& next, Steps&... steps) {
  - fn();
  + fn(what);
  next.on_error(what, steps...);
  }
  };
  