isValidModuleDest(dest) {
    return (0, (_asyncToGenerator2 || _load_asyncToGenerator()).default)(function* () {
      if (!(yield (_fs || _load_fs()).exists(dest))) {
        return false;
      }

      if (!(yield (_fs || _load_fs()).exists(path.join(dest, (_constants || _load_constants()).METADATA_FILENAME)))) {
        return false;
      }

      return true;
    })();
  }
Checker whether the folder input is a valid module folder. We output a yarn metadata
file when we've successfully setup a folder so use this as a marker.