bug#38583: [PATCH] 27.0.50; Add unattended spell-checking to checkdoc

[Eli Zaretskii]

> From: Damien Cassou <damien@cassou.me>
> Cc: bug-gnu-emacs@gnu.org, k.stevens@ieee.org, zappo@gnu.org, 
> alex.branham@gmail.com, larsi@gnus.org, eggert@cs.ucla.edu
> Date: Fri, 13 Dec 2019 20:53:43 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> > What happens if none of the spellers supported by ispell.el is
> > installed on the user's system?
> 
> Starting new Ispell process ispell with default dictionary... \ 
> Buffer xxx has no process
> 
> Emacs exit status is 255 in this case.

Can we check this up front, and display some user-friendly message to
the effect that spell-checking cannot be done?