code: function spawnChildProcess(bin, args, option) {
      const result = spawnCancelableChild(bin, args, option);
      return result.process;
  }
docs: Spawn a child process.
  
  @param  {string}    bin
  the same as the 1st argument of `child_process.spawn()`.
  @param  {Array}     args
  the same as the 2nd argument of `child_process.spawn()`.
  @param  {Object}    option
  the same as the 3rd argument of `child_process.spawn()`.
  
  @return {!PromiseLike<number>}