scripts: check-variable-fonts.sh: convert to Python

scripts: check-variable-fonts.sh: convert to Python

This script handle errors when trying to build translations
with make pdfdocs.

As part of our cleanup work to remove hacks from docs Makefile,
convert this to python, preparing it to be part of a library
to be called by sphinx-build-wrapper.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Message-ID: <d438fb01d2c00e2c2b4ac16f999d9a8ce848251b.1758196090.git.mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>