unittest pytester subprocess option tooling/usage

[RonnyPfannschmidt]

follow-up to #6444

its no longer clear if the process control option for the testsuite still works for our testsuite, we should evaluate if we want to fix/support it or drop it (breaking change for plugins using pytester)

[blueyed]

I think we do not have to dump/remove the option, only because our own tests fail with it.

[nicoddemus]

I think we do not have to dump/remove the option, only because our own tests fail with it.

Good point.

[RonnyPfannschmidt]

so how do we ensure it stays working for others?

[nicoddemus]

I would say having unittests for the option itself.