Returns the client class for the requested API version.

    :param api_name: the name of the API, e.g. 'compute', 'image', etc
    :param version: the requested API version
    :param version_map: a dict of client classes keyed by version
    :rtype: a client class for the requested API version

def get_client_class(api_name, version, version_map):
    """Returns the client class for the requested API version.

    :param api_name: the name of the API, e.g. 'compute', 'image', etc
    :param version: the requested API version
    :param version_map: a dict of client classes keyed by version
    :rtype: a client class for the requested API version
    """
    try:
        client_path = version_map[str(version)]
    except (KeyError, ValueError):
        msg = _("Invalid %(api_name)s client version '%(version)s'. must be "
                "one of: %(map_keys)s")
        msg = msg % {'api_name': api_name, 'version': version,
                     'map_keys': ', '.join(version_map.keys())}
        raise exceptions.UnsupportedVersion(msg)

    return importutils.import_class(client_path)