Steps to replicate the issue (include links if applicable):
https://en.wikipedia.org/w/index.php?title=Superbook&oldid=1148666321&unhide=1
I am an administrator and I would like to run Who Wrote That on revisions whose content has been RevisionDeleted. Instead, I get an unspecific error "Refresh or try again later".
Checking the raw request, we get a backend 500 error, so Who Wrote That? isn't wrong for a non-specific error message.
A more informative error could and should be put in WikiWho, but I can tell you it wouldn't work anyway because WikiWho can't see deleted content. The way the system works is it combs through the public revision history to build the attribution data. If any revisions are scrubbed out, it skips them. Consequently you can get somewhat inaccurate data (depending on how much content was revdel'd), since it doesn't know who to attribute that content to, but there isn't really anything we can do about that (XTools and other tools have similar issues).
Actually, what we could do at least is have Who Wrote That? check if the revision is public, and if it's not, show a more friendly error saying it can't process that revision. That is actionable and would solve it for WWT, but other clients that use WikiWho will still get nothing but a 500 response code.
Moving to our freezer as it seems like a feature enhancement, and our maintenance page dictates that features in active maintenance accept no new feature requests.