Fix for pytest 7

[hugovk]

Fixes #122.

config.inifile was deprecated so for pytest 7 check whether the new config.inipath is available first.

It's a pathlib.Path rather than a py.path.local, but we're calling str on it so that's fine.

$ ptw test_it.py

[Wed Dec  8 11:59:07 2021] Running: /Library/Frameworks/Python.framework/Versions/3.10/bin/python3 -m pytest test_it.py
========================================================== test session starts ===========================================================
platform darwin -- Python 3.10.1, pytest-7.0.0rc1, pluggy-1.0.0
rootdir: /Users/hugo/github/test
plugins: respx-0.19.0, freezegun-0.4.2, hypothesis-6.28.0, flaky-3.7.0, xdist-2.4.0, timeout-2.0.1, anyio-3.3.4, forked-1.3.0, cov-3.0.0
collected 1 item

test_it.py .                                                                                                                       [100%]

=========================================================== 1 passed in 0.06s ============================================================

[hugovk]

Closing this year old PR because this project is no longer maintained: #121