Ok, the last spurt of exceptions on the XP buildbot in the 3.x branch were all related to the fact that somehow the .hg folder in the 3.x branch build tree was missing.  The rest of the build files seemed present.  I've removed the build tree completely to let a new checkout take place and restarted the most recent build.

There does also appear to have been a test file beneath the build tree that the new clean script couldn't remove (build/test_python_580/@test_580_tmp-?L???.py).  I was able to remove it myself interactively from cmd.exe, but I've had problems like this myself when cleaning up temp files on the buildbots sometimes, and believe it has something to do with filename character encodings, depending on the tool being used to reference the file.  That might explain the non-zero error on XP though, and I agree that making sure such failures don't propagate seems right.

-- David