Bug#1061810: mathgl fails its autopkg tests with Python 3.12

[Matthias Klose]

Package: src:mathgl
Version: 8.0.1-5
Severity: important
Tags: sid trixie ftbfs
User: debian-python at lists.debian.org
Usertags: python3.12

With python3-defaults from experimental, the package fails its autopkg 
tests:

[...]
920s autopkgtest [13:46:19]: test command1: -----------------------]
920s autopkgtest [13:46:19]: test command1:  - - - - - - - - - - results 
- - - - - - - - - -
920s command1             FAIL stderr: 
/tmp/autopkgtest.QVJC2c/build.6xG/src/examples/test.py:15: 
SyntaxWarning: invalid escape sequence '\i'
920s autopkgtest [13:46:19]: test command1:  - - - - - - - - - - stderr 
- - - - - - - - - -
920s /tmp/autopkgtest.QVJC2c/build.6xG/src/examples/test.py:15: 
SyntaxWarning: invalid escape sequence '\i'
920s   gr.Puts(mglPoint(1,1,1.2),"\i f = \dfrac{1}{1+(5x-5)^2+(5y-5)^2}")
920s autopkgtest [13:46:19]: @@@@@@@@@@@@@@@@@@@@ summary
920s command1             FAIL stderr: 
/tmp/autopkgtest.QVJC2c/build.6xG/src/examples/test.py:15: 
SyntaxWarning: invalid escape sequence '\i'