plone/plone.app.users — comment on commit d684a56cd652f583ecb5db6ea6ad5a088c2fdc1d
File: plone/app/users/tests/plugins.txt line 19
By rpatterson:

Is returning a string best? Raising an error of a certain type seems more Pythonic and is also with things like zope.formlib/z3c.form validation. If there's precedent in PAS for this pattern then I say it's fine, if not I'd prefer exceptions be used. Should probably have our own exception class that subclasses ValueError.