Given a parser, load the CLI subcommands

def load_cli(subparsers):
    """Given a parser, load the CLI subcommands"""
    for command_name in available_commands():
        module = '{}.{}'.format(__package__, command_name)
        loader, description = _import_loader(module)
        parser = subparsers.add_parser(command_name,
                                       description=description)
        command = loader(parser)
        if command is None:
            raise RuntimeError('Failed to load "{}".'.format(command_name))
        parser.set_defaults(cmmd=command)