Consider removing libxml2 SAX driver

[nwellnhof]

This project seems to set the preferred XML SAX driver to drv_libxml2. This will only have an effect on a few systems where the libxml2 Python bindings are installed and could lead to non-deterministic behavior depending on the external environment.

libxml2's Python bindings and the SAX driver are outdated and will be deprecated in the long term. The libxml2 maintainers also received a report about a security issue recently. I'd strongly suggest to remove the driver from your project and rely on Python's default implementation.

[kurtmckee]

Thanks for the heads-up, Nick!