Tox: Drop the dot (py.test -> pytest)

[obestwalter]

There are 41 occurrences of py.test in the code, many of which should be replaced by pytest - some need a closer look though. There seems to be mixed usage of pytest and py.test imports in the tests -I am pretty sure this is just for historical reasons.

[obestwalter]

@davehunt - shall we do that at the next sprint? :grin:

[davehunt]

shall we do that at the next sprint?

I was actually thinking we could introduce a dot this time... t.ox anyone?

[nicoddemus]

🤣

[obestwalter]

Deal. Let me just fire up my p.y.t.h.o.n interpreter and we do this right now!