In Black Ops 3 script debug information are located inside their built FastFile**.
All you have to do in order to print any S.R.E. (script runtime error) is to set either dvar:
** NOTE: The base game doesn't have any script debuginformation, if you're getting a SRE from another script that's not built into any FastFile from your mod tools you will need to include those scripts into your zone file as well.