bug#42431: 28.0.50; browse-url-of-dired-file confusing messaging

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: michael.albinus@gmx.de,  42431@debbugs.gnu.org
> Date: Sat, 08 Aug 2020 12:05:04 +0200
> 
> >>      (condition-case ()
> >>          (let ((inhibit-read-only t))
> >>            (insert-file-contents-literally filename t))
> >>        (file-error
> >>         (when (and (file-exists-p filename)
> >>                    (not (file-readable-p filename)))
> >>           (kill-buffer buf)
> >>           (signal 'file-error (list "File is not readable"
> >>                                     filename)))
> >
> > Is this because file-readable-p returns nil for file:// URLs?
> 
> That's the direct cause of the message, but the underlying reason is
> that insert-file-contents-literally signalled a file-error here (after
> inserting the contents).  I haven't yet chased down why.

I guess that's because expand-file-name doesn't convert file:// URLs
into local file names, and then insert-file-contents chokes on the
value produced by expand-file-name.  (insert-file-contents-literally
is just a thin wrapper around insert-file-contents.)

So one solution would be to convert file:// URLs into local file names
in the above snippet, before calling insert-file-contents-literally.