Send an error message to the active client. The new error will be
            displayed on any active GUI clients.

            Args:
                message (str): Plain-text message to display.

            Returns:
                None

            >>> s = _syncthing()
            >>> s.system.show_error('my error msg')
            >>> s.system.errors()[0]
            ... # doctest: +ELLIPSIS
            ErrorEvent(when=datetime.datetime(...), message='"my error msg"')
            >>> s.system.clear_errors()
            >>> s.system.errors()
            []

def show_error(self, message):
        """ Send an error message to the active client. The new error will be
            displayed on any active GUI clients.

            Args:
                message (str): Plain-text message to display.

            Returns:
                None

            >>> s = _syncthing()
            >>> s.system.show_error('my error msg')
            >>> s.system.errors()[0]
            ... # doctest: +ELLIPSIS
            ErrorEvent(when=datetime.datetime(...), message='"my error msg"')
            >>> s.system.clear_errors()
            >>> s.system.errors()
            []
        """
        assert isinstance(message, string_types)
        self.post('error', data=message)