The ResourceWarning was added by Issue 26741.

I agree that there are legitimate reasons why pre-3.6 code may avoid calling Popen.wait() and equivalent. Victor opened Issue 27068 about adding a Popen.detach() method, which such code could use to opt out of the warning.

I don’t think there should be a special exemption for the warning at shutdown time. I think we should either:

1. Accept that you should never destroy a 3.6 Popen object without first “waiting” on its child (or zombie), or:

2. Revert the warning, and in a future release (e.g. 3.7), add it back along with a way to opt out of the warning.