message: [now-cli] Catch `process.kill()` for dev process and mute "ESRCH"
  "ESRCH" error means that the process is no longer running, and thus
  already shut down. No need to throw in that case so just ignore the
  error.
  Fixes:
diff: @@ -867,6 +867,7 @@ export default class DevServer {
  * Shuts down the `now dev` server, and cleans up any temporary resources.
  */
  async stop(exitCode?: number): Promise<void> {
  + const { devProcess } = this;
  if (this.stopping) return;
  this.stopping = true;
  @@ -883,17 +884,22 @@ export default class DevServer {
  ops.push(shutdownBuilder(match, this.output));
  }
  + if (devProcess) {
  ops.push(
  - new Promise(resolve => {
  - if (!this.devProcess) {
  - resolve();
  - return;
  + new Promise((resolve, reject) => {
  + devProcess.once('exit', () => resolve());
  + try {
  + process.kill(devProcess.pid);
  + } catch (err) {
  + if (err.code === 'ESRCH') {
  + // Process already exited
  + return resolve();
  + }
  + reject(err);
  }
  -
  - this.devProcess.on('exit', () => resolve());
  - process.kill(this.devProcess.pid, exitCode);
  })
  );
  + }
  ops.push(close(this.server));
  