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

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Tue, 28 Jul 2020 00:24:23 +0200
> Cc: Michael Albinus <michael.albinus@gmx.de>
> 
> (browse-url-of-file "/tmp/a.txt")
> 
> The message originates from here, sort of:
> 
> (defun find-file-noselect-1 (buf filename nowarn rawfile truename number)
> 
> [...]
> 
>         (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?