Summary
os.waitstatus_to_exitcode is available from python 3.9 and should only be used where available.

Motivation

• Does this affect any team outside of WT?
  Not blocked, but could fail python tests.

• How likely is it that this use case or problem will occur?
  Limited impact as its only when checking for child process failures.

• If the problem does occur, what are the consequences and how severe are they?
  A minor annoyance.

• Is this issue urgent?
  No

Acceptance Criteria (Definition of Done)
The function is only used when available.