Someone recently reported a bug in Gnus for searching IMAP groups when
the group has a non-ascii name. The bug has been there a while, at least
as far back as Emacs 26. I've attached the diff, which looks large only
because of indentation changes, it boils down to adding the line:

(setq group (nnimap-decode-gnus-group group))

Is it too late/too intrusive for Emacs 26? This is the first time
anyone's reported the bug, so it's obviously not super pressing. Another
odd thing is that this fix will be unnecessary once the
scratch/gnus-decoded branch lands, so this change shouldn't go into
master, but I gather that's possible with a dontmerge cookie or
something.

Anyway, just asking!

Eric