Infinite recursion in the tokenizer when emitting invalid escape sequence warnings

[lysnikolaou]

Checklist

• I am confident this is a bug in CPython, not a bug in a third-party project
• I have searched the CPython issue tracker,
  and am confident this bug has not been reported before

CPython versions tested on:

3.12, CPython main branch

Operating systems tested on:

macOS

Output from running 'python -VV' on the command line:

Python 3.11.3 (main, May 8 2023, 13:16:43) [Clang 14.0.3 (clang-1403.0.22.14.1)]

A clear and concise description of the bug:

The tokenizer has an infinite recursion when emitting an invalid escape sequence SyntaxWarning. This was probably introduced in #106993. Fix will be up shortly.

Linked PRs

• gh-107967: Fix infinite recursion on invalid escape sequence warning #107968
• [3.12] gh-107967: Fix infinite recursion on invalid escape sequence warning (GH-107968) #107970