As per https://peps.python.org/pep-0394/, the python binary can be one
of the following options:
- Python 2
- Python 3
- Not exist
All of the scripts in libxml2 use 'python', which may not exist.
As Python 2 reached EOL on the 1st January 2020, it's safe to move the
scripts to use python3 explicitly.
* parser.c: fixing #109227 providing more context in case of
start/end tag mismatch
* python/tests/ctxterror.py python/tests/readererr.py: update the
tests accordingly
Daniel
* xmlreader.c python/drv_libxml2.py python/generator.py
python/libxml.c python/libxml.py python/libxml_wrap.h
python/types.c: patch from Stphane Bidoul for better per
context error message APIs
* python/tests/ctxterror.py python/tests/readererr.py:
update of the tests
Daniel