def _add_project_filter_auth_role_arg(arg_parser):
    """
    Adds optional auth_role filtering parameter to a parser.
    :param arg_parser: ArgumentParser parser to add this argument to.
    """
    help_text = "Filters project listing to just those projects with the specified role. "
    help_text += "See command list_auth_roles for AuthRole values."
    arg_parser.add_argument("--auth-role",
                            metavar='AuthRole',
                            type=to_unicode,
                            dest='auth_role',
                            help=help_text,
                            default=None)
Adds optional auth_role filtering parameter to a parser.
    :param arg_parser: ArgumentParser parser to add this argument to.