Yet another Python wrapper for PAM

There seems to be a glut of Python wrappers for PAM that have since been abandoned. This repo merges two separate efforts:

- [gnosek/python-pam](https://github.com/gnosek/python-pam) - adds wrappers for a few more calls, e.g. opening sessions - raises PamError on failure instead of returning False, with informative error messages - [simplepam](https://github.com/leonnnn/python3-simplepam) - adds Python 3 support - resets credentials after authentication, apparently for kerberos users