Raise appropriate error message when user's private role is missing on purge

        if not user.deleted:

            raise exceptions.MessageException("User '%s' has not been deleted, so they cannot be purged." % user.email)

        private_role = self.app.security_agent.get_private_user_role(user)

        if private_role is None:

            raise exceptions.InconsistentDatabase(

                "User '%s' private role is missing while attempting to purge deleted user." % user.email

            )

        # Delete History

        for active_history in user.active_histories:

            self.session().refresh(active_history)