bug#33510: 26.1.90; M-x man crashes if invoking man fails

[Eli Zaretskii]

> From: Richard Copley <rcopley@gmail.com>
> Date: Mon, 26 Nov 2018 12:34:41 +0000
> 
> If invoking 'man' fails, M-x man crashes, with errors:
>   error in process sentinel: read-event: Buffer is read-only: #<buffer *Man 
> xyzzy*>
>   error in process sentinel: Buffer is read-only: #<buffer *Man xyzzy*>

Signaling an error is a far cry from a crash...

> To reproduce from 'emacs -Q':
> M-x man RET
> xyzzy RET

I cannot reproduce this, at least not on GNU/Linux: there, I get

  Can't find the xyzzy manpage

as expected.  On MS-Windows I get this instead:

  No manual entry for xyzzy.

So I think the problem is triggered by something done by the 'man'
port you have installed (an MSYS2 'man', perhaps?).  What does it say
if you invoke it from the shell prompt?