address bug AttributeError: 'PseudoKeyReference' object has no attribute 'constraint_name'
address bug AttributeError: 'PseudoKeyReference' object has no attribute 'constraint_name'

This was an order of initialization bug for a corner case of pseudo foreign key
constraints added to the DB via a local DBA.

informatics-isi-edu/ermrest,informatics-isi-edu/ermrest