If Bill gets a chance to investigate this before the weekend, great, otherwise my plan to stop making noise in the buildbot results will be to:

1. Create a separate issue specifically for the errors reported by the Mac OS X buildbots (allowing the problem to be spelled out more clearly for readers, and also allowing the feature request itself to be closed)

2. Flag the offending tests as expected failures on Mac OS X, with a pointer back to the new tracker issue.

That way, if these failures are due to underlying OS bugs or limitations (as they appear to be), we'll get a clear indication in the buildbots when Apple have fixed the relevant problems.