Convenience method for showing an error dialog.

def show_error_dialog(self, message, details=None):
        """
        Convenience method for showing an error dialog.
        """
        dlg = Gtk.MessageDialog(type=Gtk.MessageType.ERROR, buttons=Gtk.ButtonsType.OK,
                                 message_format=message)
        if details is not None:
            dlg.format_secondary_text(details)
        dlg.run()
        dlg.destroy()