It looks like there's already some code in place to work around the subprocess._cleanup issue in runxpcshelltests.py. It looks like the issue is that not all of the popen calls have had the work around applied, or maybe the guard for the current workaround isn't quite right, because when I bashed it into place everywhere in that file [I finally got a green Win7 run](https://treeherder.mozilla.org/jobs?repo=try&revision=8095566ef417ea272283294f301883a71b556f56&selectedTaskRun=Dcb_hhmXSd2LGdNKwXIJ7g.0). I'll probably do that in a separate bug blocking this one.
Bug 1769791 Comment 35 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
It looks like [there's already some code in place](https://searchfox.org/mozilla-central/rev/5c04fc7016eb7f52cf835d482f1125c8f139c959/testing/xpcshell/runxpcshelltests.py#298-309) to work around the subprocess._cleanup issue in runxpcshelltests.py. It looks like the issue is that not all of the popen calls have had the work around applied, or maybe the guard for the current workaround isn't quite right, because when I bashed it into place everywhere in that file [I finally got a green Win7 run](https://treeherder.mozilla.org/jobs?repo=try&revision=8095566ef417ea272283294f301883a71b556f56&selectedTaskRun=Dcb_hhmXSd2LGdNKwXIJ7g.0). I'll probably do that in a separate bug blocking this one.