This appears to have spontaneously resolved itself after build #957 after many failures. For reference, other builders on the same host were failing as well:

AMD64 FreeBSD CURRENT Debug 3.5 (#567, #568)
AMD64 FreeBSD CURRENT Non-Debug 3.5 (#8, #9)

And possibly others (Didn't listed any that hadn't failed in the last 5 builds)

According to my (non-expert) reading of the code, the test skips (or is supposed to skip) unless group count of uid is > 1.

The group membership of the buildbot user this worker runs as is only 'buildbot' and on that basis wouldn't a skip expected?

Open questions are:

1) Why/how did it suddenly *start* failing. (I cant see any relevant commits at or around the time)
2) Why/how did it suddenly stop failing (I made no worker/buildbot changes

Nosy vajrasky (original unit test creator) and Claudiu (who reviewed), who might be able to shine a light on what might be going on