code: public static FileNotFoundException getFileNotFoundException(
        String bucketName, String objectName) {
      checkArgument(!isNullOrEmpty(bucketName), "bucketName must not be null or empty");
      return new FileNotFoundException(
          String.format(
              "Item not found: '%s'."
                  + " If you enabled STRICT generation consistency, it is possible that"
                  + " the live version is still available but the intended generation is deleted.",
              StorageResourceId.createReadableString(bucketName, nullToEmpty(objectName))));
    }
docs: Creates FileNotFoundException with suitable message for a GCS bucket or object.