'Retrieve the latest hosts data file.
.. note:: This method is the slot responses to the signal from
ButtonUpdate widget while the button is clicked.
This method would call operations to
.. note:: Method :meth:`~gui.qdialog_slots.on_CheckUpdate_clicked`
would be called if no update information has been set,
.. note:: If the current data is up-to-date, no data file would be
retrieved.'

def on_FetchUpdate_clicked(self):

    self.set_fetch_click_btns()
    self._down_flag = 1
    if ((self._update == {}) or (self._update['version'] == unicode(_translate('Util', '[Error]', None)))):
        self.check_update()
    elif self.new_version():
        self.fetch_update()
    else:
        self.info_uptodate()
        self.finish_fetch()
