Pythia8 Version Update, 21.6 branch (2019.09.23.) (!26750) · Merge requests · atlas / athena · GitLab

Attila Krasznahorkay requested to merge akraszna/athena:Pythia8Update-21.6-20190923 into 21.6 Sep 23, 2019

This updates AthGeneration to Pythia8 243p4. This is to fix the issue discussed in https://sft.its.cern.ch/jira/browse/SPI-1459.