public function maintenance_mode_warning($maintenancemode) {
        if (!$maintenancemode) {
            return '';
        }

        $url = new moodle_url('/admin/settings.php', array('section' => 'maintenancemode'));
        $url = $url->out(); // get_string() does not support objects in params

        return $this->warning(get_string('sitemaintenancewarning2', 'admin', $url));
    }