expdate was not getting copied for Invitation class
@@ -813,6 +813,7 @@ class Invitation(object):
tcdate = i.get('tcdate'),
tmdate = i.get('tmdate'),
duedate = i.get('duedate'),
+ expdate = i.get('expdate'),
readers = i.get('readers'),
nonreaders = i.get('nonreaders'),
writers = i.get('writers'),
