Message 262787 - Python tracker

Got f_lasti working as -1. Applied PEP7. Unrelated: fixed a misnamed variable in test_grammar because it ran into a peephole bug (const -> jump_if_false erase didn't work when EXTENDED_ARGs were involved). dis has argval/arg set to None instead of the unused argument value

Things are seeming more brittle with f_lasti as -1. But maybe it's all in my head