Yes, it currently raises a No method defined for short_predicate.  I have no clue what to be expecting in the solr hash, I just want the hash to be generated.  AS 6.6 has some non backward compatible changes, including the removal of short_predicate,ActiveFedora::RelsExtDatastream.  I would not have expected that type of change between 6.0 and 6.6.  This is to get around that.