Hi David,
I have no idea. It was done 5 years ago. Perhaps for a given version of pythia6 the function didn’t exists. I have checked and for latest version 429 the function seems to be there. Can you please and uncomment and check if it is OK.
Sorry. I tagged the version on Friday and only announced today (still we have some manual action in the release procedure). So it was too late. Another one in a few weeks