Log Message:
py-rarfile: updated to 3.1

Version 3.1:

This will be last version with support for Python 2.x

New feature:
Accept pathlib objects as filenames.
Accept bytes filenames in Python 3

Fixes:
Use bug-compatible SHA1 for longer passwords (> 28 chars) in RAR3 encrypted \ 
headers.
Return true/false from _check_unrar_tool
Include all test files in archive
Include volume number in NeedFirstVolume exception if available (rar5).

Cleanups:
Convert tests to pytest.