The problem was already present with python versions <= 3.11, but only appeared
at runtime. From python 3.12 onwards it becomes possible to statically reproduce
it by forcing a bytecode compilation.

The change is useful for future-proofing the code base, since future python
versions will start to exit with a runtime exception.

From https://docs.python.org/3/whatsnew/3.12.html#other-language-changes :
    A backslash-character pair that is not a valid escape sequence now generates
    a SyntaxWarning, instead of DeprecationWarning. For example,
    re.compile("\d+\.\d+") now emits a SyntaxWarning ("\d" is an invalid escape
    sequence, use raw strings for regular expression: re.compile(r"\d+\.\d+")).
    In a future Python version, SyntaxError will eventually be raised, instead
    of SyntaxWarning.

Command to reproduce the problem:
    find . -name "__pycache__" -print0 | xargs -0 rm -rf && python3.12 -B -m compileall -q .

Here the removal of __pycache__ is just a hackish way of forcing a bytecode
regeneration.

--HG--
branch : stable