Message 337281 - Python tracker

They weren't *intended* to change it, and didn't in the original implementation of the PEP, but they do in the as-shipped Python 3.7 implementation, and I abandoned my attempts to revert to the as-designed behaviour as impractical given the other changes made for PEP 540. So that's a behavior we're stuck with now: they both have global side effects on the locale of the calling process.