Improved error reporting for CPython 3.10—and beyond

> I have never met a (not-Lisp) expansion language that I actually liked. I'm not sure why programmers keep trying to build them.

For TeX it was simply because a typesetting language should have *typesetting text* as its primary purpose: so its primary input should be that text, not function calls or whatever. This more or less forces macro-expansion, or something like it, as a way to get anything but text in there. Ugly as sin, but there you are. :/