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.
* python/generator.py python/libxml.c python/libxml.py
python/libxml2-python-api.xml python/libxml2class.txt
python/libxml_wrap.h python/types.c: updated the python
bindings, added code for easier File I/O, and the ability to
define a resolver from Python fixing bug #91635
* python/tests/Makefile.am python/tests/inbuf.py
python/tests/outbuf.py python/tests/pushSAXhtml.py
python/tests/resolver.py python/tests/serialize.py: updated
and augmented the set of Python tests.
Daniel
