i tested a python script works with pythin2.7x version and used the same script to run in python3, which returns error code 1.
it works in python2.7x
below is the commands.conf
[prettyformat]filename = xmlformat.pyretainsevents = trueoverrides_timeorder = falserun_in_preview = falsestreaming = truepython.version = python3
There are many reasons why a script would return error code 1 and the information supplied doesn't begin to offer enough information to suggest a solution.
Is the script syntactically compliant with Python3?
Have you checked it with the Splunk Upgrade Readiness app?
What errors are reported in the search log?