Sorry, I realize what's wrong here. When we switched to the new PEG parser (the "pegen" you saw mentioned in the warning) we switched to a new grammar file. You have to change Grammar/python.gram instead of Grammar/Grammar.

We couldn't get rid of the Grammar/Grammar file yet because it's mentioned in the docs; this is pending a better way of producing https://docs.python.org/3.10/reference/grammar.html.

I hope this has informed you sufficiently; I don't think there's a bug that needs to be fixed on our end.