From a PDI job , I'm wondering about how to get Error Messages may have been thrown by a sub-job or sub-transformation.

I'm talking about the KettleException case described in

The message I'd like to get (to send it by email for instance), is the first ERROR log.. the one which caused the called ktr/kjb to fail.
So indeed, it is in the logs but It is not so easy to retrieve from there (unless making it log in a distinct file... which I'd try to avoid as much as possible).
I have dreamt about finding this in the job's variables.. something like ${KettleException.message} unfortunately without success.

Is there a best practice solution to this situation ?