Set an environment variable with current test

[nicoddemus]

When executing tests in CI, sometimes a test may hang indefinitely. One can look at the output using -v but that might not always be reliable.

If each worker would set a specific environment variable with the test it is executing, one can use a process monitoring library like psutil to figure out which worker is running which test. This could be a variable named something like PYTEST_XDIST_CURRENT_TEST which is set to the test node id. Alternatively, we could also add if the test is in the setup, call or teardown phase.

The implementation should be trivial and can be really helpful when diagnosing CI problems.

@RonnyPfannschmidt what do you think?

[RonnyPfannschmidt]

@nicoddemus this should go to core pytest, as its helpfull even for a non-xdist hang

[nicoddemus]

Hmm good point. Will create an issue there.

[nicoddemus]

Closed in favor of pytest-dev/pytest#2583