gistfile1.txt

cancel_icon = Icon(icon_name='dialog-cancel')
        cancel_label = _('Continue download')
        alert.add_button(Gtk.ResponseType.CANCEL, cancel_label,
                         cancel_icon)
        stop_icon = Icon(icon_name='dialog-ok')
        alert.add_button(Gtk.ResponseType.OK, _('Stop'), stop_icon)
        stop_icon.show()
        activity.add_alert(alert)
        alert.connect('response', self.__response_cb, activity)
        alert.show()
        activity.present()

        def __response_cb(self, alert, response_id, activity):
        activity.remove_alert(alert)
        if response_id is Gtk.ResponseType.CANCEL:
            activity.close()
        elif response_id == Gtk.ResponseType.OK:
            activity.close()