Run NodeJS child_process.spawn() with Promise

promised_spawn.js

// Run spawn as promised
function promised_spawn(cmd, args, option) {
   let deferred = Q.defer();
   let watch = child_process.spawn(cmd, args, option);
   watch.on('error', (error) => {
      deferred.reject('encountered error ' + error.message);
   })
   .on('exit', (code) => {
      if (code !== 0) {
         deferred.reject('exited with code ' + code);
      } else {
         deferred.resolve();
      }
   })
   .on('close', (code) => {
      if (code !== 0) {
         deferred.reject('exited with code ' + code);
      } else {
         deferred.resolve();
      }
   });
   watch.stdout.on('data', (data) => {
      // Print to console directly
      process.stdout.write(data.toString());
   });
   watch.stderr.on('data', (data) => {
      process.stdout.write(data.toString());
   });
   return deferred.promise;
}