Drop _pytest._compat in favor of six

[nicoddemus]

As stated in the mailing list, check if it would be worthwhile in respect to remove custom code and make it easier for contributors.

[crazymerlyn]

compat.py seems to have collected quite a few utility functions like getlocation and getfuncargnames which aren't related to six. Is there still interest in dropping this module?

[nicoddemus]

Hi @crazymerlyn thanks for revisiting this.

I don't think it will be the case indeed. We will probably clean _pytest.compat up quite a bit when dropping Python 2 anyway.

I'm closing this then. 👍