'Initialize command line argument parser.
Args:
parser: argparse.ArgumentParser'

@classmethod
def initArgumentParser(cls, parser, defaults=None):

    parser.add_argument('--gcs_json_path', default='', help='The    path    to    the    Google    Cloud    Storage    service    credentials    JSON    file.')
    parser.add_argument('--gcs_bucket', default='', help="The    name    of    the    Google    Cloud    Storage    bucket    to    use,    e.g.    'spinnaker-bucket'.")
    parser.add_argument('--gcs_base_path', default='', help="The    root    folder    in    the    specified    Google    Cloud    Storage    bucket    to    place    all    of    Spinnaker's    persistent    data.")
    super(GoogleFront50TestScenario, cls).initArgumentParser(parser, defaults=defaults)
