Wonderful. That means we're ready to release ASDF 3.3.0, at long last. Just 6 months after schedule. But better and stronger, like a 3.3.2 would have been.
I tracked the error down to the custom iolib.pr42.66ea927 staying in quicklisp/local-procects since I used it to test asdf.3.3.0-rc1.a6bd7c6.Removed it; restarting he tests with clean quicklisp.