bug#37950: 27.0.50; File error regression

[Juri Linkov]

0. emacs -Q

1. in Dired type 'v' ('dired-view-file') to view a read-protected file, e.g.
   from non-root to visit a file with such permissions: -rw------- root root

2. Empty buffer is displayed (but the file size is several kilobytes)

3. The echo area displays the message:

   View mode: type C-h for help, h for commands, q to quit.

4. Visiting *Messages* reveals the error message:

   Note: file is write protected

obscured by the View mode message above.

But this error message is wrong anyway.  In previous versions
the error message was correct:

    find-file-noselect-1: File is not readable:

and it rightfully refused to visit the read-protected file.


In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2019-10-27 built on localhost
Repository revision: c6667cc6a958e06fd43fb1ee0e80753adfefa49d
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Linux Mint 19

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Note: file is write protected
View mode: type C-h for help, h for commands, q to quit.

Configured using:
 'configure --with-x-toolkit=gtk3 --with-xwidgets --with-xft
 --with-modules --enable-checking=yes,glyphs
 --enable-check-lisp-object-type 'CFLAGS=-O0 -g3 -gdwarf-4''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GSETTINGS GLIB NOTIFY INOTIFY
GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS PDUMPER
LCMS2 GMP

Important settings:
  value of $LC_MONETARY: et_EE.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_DK.utf8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix