fix generation of unknown casstype objects
fix generation of unknown casstype objects

since class names have to be bytes, not unicode

josh-mckenzie/cassandra-dbapi2,pandu-rao/cassandra-dbapi2,iflatness/cql,mshuler/cassandra-dbapi2,stanhu/cassandra-dbapi2,CanWeStudio/cassandra-dbapi2,EnigmaCurry/cassandra-dbapi2,iGivefirst/cassandra-dbapi2,diezguerra/cassandra-dbapi2,maraca/cassandra-dbapi2,flowroute/cassandra-dbapi2,pcmanus/python-cql