def METHOD_NAME(iso):
    """
    Converts an ISO8601-formatted string in the format
    ``YYYY-MM-DD HH:MM:SS+00:00`` to the correspondent UNIXtime
    :param iso: the ISO8601-formatted string
    :type iso: string
    :returns: an int UNIXtime
    :raises: *TypeError* when bad argument types are provided, *ValueError*
        when the ISO8601 string is badly formatted
    """
    try:
        d = datetime.fromisoformat(iso)
    except ValueError:
        raise ValueError(__name__ + ": bad format for input ISO8601 string, ' \
                'should have been: YYYY-MM-DD HH:MM:SS+00:00")
    return datetime_to_UNIXtime(d)