Database error on /cat/api/1.0/list-machines/

We fixed the main source of this oops with bug 1169225 by not saving the first/last names (displayname) as it is not used. However, we're still seeing some oopses with a different traceback that indicate that the username we are saving is > 30 chars. From a sample oops [1] this shouldn't be the case (the LP username in this case is, afaics, rcpao):

[1] https://oops.canonical.com/oops/?oopsid=031c0e8f01a34ff783b1d5bfd64206e7