Comment 2 for bug 1859844

Snip from assemble method:

        try:
            b_domain_id = cls.convert_uuid_hex_to_bytes(domain_id)
        except ValueError:
            # the default domain ID is configurable, and probably isn't a UUID
            if domain_id == CONF.identity.default_domain_id:
                b_domain_id = domain_id
            else:
                raise

Note explicit catch of ValueError to deal with configurable default domain ID and not being a UUID.