[Helium] inaccurate error message when local helium bundle path is invalid (HeliumBundleFactory)

ERROR [2017-03-05 12:54:14,308] ({qtp1121647253-68} HeliumBundleFactory.java[buildBundle]:131) - Can't get module name and version of package zeppelin-markdown-spell

if (isLocalPackage(pkg)) {
      File packageJson = new File(artifact, "package.json");
      if (!packageJson.isFile()) { // here
        return null;
      }