Uppercase in username breaks things

[wdoekes]

$ pstore someobj ^user-OLD
['user-old']   # <-- 'revoke' in pstore
dict_keys(['alex', 'user-OLD', 'herman', 'jordi', 'ronald', 'walter'])
user error: one or more users cannot be revoked

Probably goes sour in other places as well. Use django-model-validator to ensure that username is lowercase?