'Remove expired instances of this manager\'s object class.
Accounts to be deleted are identified by searching for
instances of this manager\'s object class with expired activation
keys, and then checking to see if their associated ``User``
instances have the field ``is_active`` set to ``False``; any
``User`` who is both inactive and has an expired activation
key will be deleted.'

def delete_expired_users(self):

    days_valid = settings.ACCOUNT_ACTIVATION_DAYS
    expired = (datetime.now() - timedelta(days=days_valid))
    prof_ids = self.filter(user__date_joined__lt=expired)
    prof_ids = prof_ids.values_list('id', flat=True)
    for chunk in chunked(prof_ids, 1000):
        _delete_registration_profiles_chunk.apply_async(args=[chunk])
