private function allowed_tags_message($badtag) {
        $a = new stdClass();
        $a->tag = htmlspecialchars($badtag);
        $a->allowed = $this->get_list_of_printable_allowed_tags($this->allowedhtmltags);
        if ($a->allowed) {
            return get_string('tagsnotallowed', 'qtype_gapselect', $a);
        } else {
            return get_string('tagsnotallowedatall', 'qtype_gapselect', $a);
        }
    }