Message 308113 - Python tracker

Serhiy: how are you supposed to modify local variables of a frame when these variables are stored in "fast locals"? Even if it's a rare useful, I think that it's ok to expose PyFrame_FastToLocalsWithError(), and maybe also PyFrame_FastToLocals().

It is useful you want write a debugger in pure C, and don't want to bother with fast locals special case.