python-markdown's `version_info` is deprecated

`version_info` attribute of python-markdown has been deprecated via:
https://github.com/Python-Markdown/markdown/commit/a767b2daaad78ba32d45a4f1dabb7c5e218f030a

There are several lines in this repository that access that attribute, and this module does not work with python-markdown 3.4.