Fail to build with python 3.12

[f-zl]

The dependency package litex 2023.12 uses escape sequences like \$ \+ (at e.g. litex/soc/cores/cpu/cv32e40p/core.py:68), which are invalid in python 3.12.
The most recent litex 2024.12 installed by pdm add litex still has this problem.
How to fix this? Thanks very much!