@Override
  public void validateOutputFilePrefixSupported(String filePrefix) {
    verifyPath(filePrefix);
    verifyPathIsAccessible(filePrefix, "Output path does not exist or is not writeable: %s");
  }
@Test
  public void testOutputPrefixMissingBucket() {
    expectedException.expect(IllegalArgumentException.class);
    expectedException.expectMessage(
        "Missing object or bucket in path: 'gs://output/', "
            + "did you mean: 'gs://some-bucket/output'?");
    validator.validateOutputFilePrefixSupported("gs://output");
  }