message: always send the sender
diff: @@ -21,9 +21,18 @@ import FatalError from "../errors/fatal";
  export function sendMessage(id, payload) {
  return browser.runtime.sendMessage(id, payload).then((response) => {
  if (response.error) {
  - return Promise.reject(response.status === "fatal" ? new FatalError(response.error) : new Error(response.error));
  + const error = response.status === "fatal" ? new FatalError(response.error) : new Error(response.error);
  + error.sender = id;
  + return Promise.reject(error);
  } else {
  - return Promise.resolve(response);
  + const r = {};
  + if (typeof response === "string") {
  + r.message = response;
  + } else if (response instanceof Object) {
  + Object.assign(r, response);
  + }
  + r.sender = id;
  + return Promise.resolve(r);
  }
  }).catch((response) => {
  if (isReceivingEndError(response)) {
  