def get_authorization_header(id_token):
    """Generate authorization http request header.

    Args:
        id_token (str): The id token.
    Returns:
        A dict contains 'Authorization'.
    Raises:
        Exception: No id token provided.
    """
    if not id_token:
        raise Exception('Unauthorized.')
    return { 'Authorization': 'Bearer ' + id_token }