Returns a warning message when there is no data about available updates.
function _update_no_data() {
$destination = drupal_get_destination();
return t('No update information available. <a href="@run_cron">Run cron</a> or <a href="@check_manually">check manually</a>.', array(
'@run_cron' => url('admin/reports/status/run-cron', array(
'query' => $destination,
)),
'@check_manually' => url('admin/reports/updates/check', array(
'query' => $destination,
)),
));
}