bug#68213: 30.0.50; completion-preview-tests failure in --without-x build

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Eli Zaretskii <eliz@gnu.org>,  jm@pub.pink,  68213@debbugs.gnu.org
> Date: Sun, 07 Jan 2024 12:15:25 -0500
> 
> > IIUC, `defvar-keymap` is not flexible enough to support this use case,
> > or any case in which the programmer cannot guarantee in advance that all
> > keys are distinct, which they can mostly do only if all keys are static.
> 
> Yeah, I think signaling an error like we do now is a bit drastic.
> Why not demote it to a warning?

I don't mind, but that's a separate issue.  Even a warning in running
a test is something we should avoid, so I'm interested in solving that
problem first.