def METHOD_NAME(request):
    cmd_packages_path = request.config.getoption("--" + packages_path_arg_posix, None)
    if not cmd_packages_path:
        raise ValueError("Could not determine packages installation path. "
                         "Either define it in the env variable %r, or pass it as an "
                         "argument with `--%s`" %
                         (packages_path_env, packages_path_arg_posix))
    return cmd_packages_path