docs: function bundle(location, opts, callback) {
      var b
      if (opts.watchify) {
          b = getFromCache(location, opts);
      } else {
          b = getBundle(location, opts)
      }
  
      b.bundle(function onPayload(err, payload) {
          if (err) {
              return callback(err);
          }
  
          payload = embedNodeEnv() + payload;
  
          callback(null, payload);
      });
  }