bug#34093: auto-save prevents quitting emacs on read-only filesystem

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Tue, 18 Aug 2020 17:52:24 +0000
> Cc: 34093@debbugs.gnu.org
> 
> (progn (savehist-mode)
>        (setq savehist-file "/usr/foo")
>        (confirm-exit-emacs))
> 
> I have attached a patch which fixes this bug by showing a warning if
> this file is not readable.

Thanks, but is a single warning really enough?  What if the situation
is slightly different, in that the user could somehow resolve the
problem -- should we perhaps prompt the user whether to retry or
ignore the error?