Comment 2 for bug 734847

I changed a little the phpdoc for Task::render() in r942.
Called by Job::execute() and Job::executeNext(), Task::render() returns a HTML code which will be included into the email body and into a notification, shown to the user if the browser is active, after
 "Démon de création de fichier XLS : L'exécution de la tâche n°216 s'est finie le 14 mar 2011 14:44:00."
and before
 "Cordialement"

As you can see in the quoted email, it is already the case, the string
 "The zip file has been correctly processed"
comes from XlsTask.

If you prefer not to use the default layout, you can change Job::execute() and Job::executeNext() to not send email and notifications when Task::render() returns false.