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!

[martinling]

Although I got SyntaxWarning warnings about those escape sequences, I was just now able to build current main (at e416cd5b) with Python 3.12.

When I tried building the same commit with Python 3.13 I got the error Cannot extract CSR name from code, need to specify. That seems to relate to enjoy-digital/litex#2152 (reported here as #29).