Not sure if this can be done.
The email templates in the System Setup for the QlikView Distribution Service (QDS) for the failure event set the format of the email message.
The standard format does include a reference to part of the log being included and adds a field [Log], but this is the QDS log and not the document log.
A QDS log is always created, but the document log only exists if the generate log file option is enabled on the document properties of the source QVW.
If the generate log file is not selected then there is only the QDS log available and there is no document log detailing what happened in the load script..