More detailed login failures on linelog

I have been playing around with linelog in order to send all the status via rsyslog to a remote machine and it has been working pretty well. What I still don't manage to get is how to have more detailed authentication failure messages in order to troubleshoot what went wrong. I'm currently using %{Module-Failure-Message}, but i only get stuff like "EAP module failure" instead of something more useful like "username is not found in ldap" or "Password incorrect" How can I do this? Thanks!