[Linux] psutil.tests.test_posix.TestProcess.test_nice fails under non-realtime scheduling policy about psutil HOT 2 OPEN

Does this mean Process.nice() is wrong or the test is wrong?
Should Process.nice() behave differently and take into account group scheduling (how?)?

from psutil.

Does this mean Process.nice() is wrong or the test is wrong? Should Process.nice() behave differently and take into account group scheduling (how?)?

To be honest I'm not sure what the correct solution is, that's why I opened this as an issue rather than a PR. I think the only real issue here is with SCHED_IDLE. From sched(7):

(Since Linux 2.6.23.) SCHED_IDLE can be used only at static priority 0; the process nice value has no influence for this policy.
This policy is intended for running jobs at extremely low priority (lower even than a +19 nice value with the SCHED_OTHER or SCHED_BATCH policies).

Perhaps we should mirror ps(1) logic and return None or "-" for any policy other than SCHED_OTHER or SCHED_BATCH?

from psutil.