message: fix unkillable ember-cli
  This was causing `ember s` or `ember test` to hang after exceptions while ignoring SIGINT.
diff: @@ -158,12 +158,21 @@ module.exports = {
  // dev server your session gets invalidated.
  let sessionsKey = crypto.randomBytes(32);
  + try {
  let koaApp = await makeServer(this.project.root, sessionsKey, seedModels, {
  allowDevDependencies,
  broccoliConnector: this._broccoliConnector,
  emberConfigEnv: require(this.project.configPath())(env)
  });
  return koaApp.callback();
  + } catch (err) {
  + // we don't want to leave our broccoli build hanging forever,
  + // because ember-cli waits for it to exit before doing its own
  + // cleanup and exiting, meaning we could get an unkillable
  + // ember-cli.
  + this._broccoliConnector.setSource(Promise.reject(err));
  + throw err;
  + }
  }
  };
  