bug#16062: 24.3; Missing .png file gives poor error message when opened

[Alex Willisson]

When I try to open a .png file which does not exist, I get the error
message "Cannot display image: (Cannot determine image type)" in the
minibuffer, instead of something more related to "File does not exist"

Steps for reproduction:

$ emacs -Q

C-x C-f not_an_actual_file.png <return>

This bug looks like it occurs for nearly all image extensions, I have
reproduced it with these extensions: .png, .gif, .jpeg, .jpg, .ppm,
.pnm, .tiff, .xpm, .xcf, .psd, .bmp, .tga, .ico, .rgb, and .svg.

In GNU Emacs 24.3.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.9.10)
 of 2013-08-14 on buildvm-17.phx2.fedoraproject.org
Windowing system distributor `Fedora Project', version 11.0.11402000
System Description:    Fedora release 20 (Heisenbug)

Configured using:
 `configure '--build=x86_64-redhat-linux-gnu'
 '--host=x86_64-redhat-linux-gnu' '--program-prefix='
 '--disable-dependency-tracking' '--prefix=/usr' '--exec-prefix=/usr'
 '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc'
 '--datadir=/usr/share' '--includedir=/usr/include'
 '--libdir=/usr/lib64' '--libexecdir=/usr/libexec'
 '--localstatedir=/var' '--sharedstatedir=/var/lib'
 '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--with-dbus'
 '--with-gif' '--with-jpeg' '--with-png' '--with-rsvg' '--with-tiff'
 '--with-xft' '--with-xpm' '--with-x-toolkit=gtk3' '--with-gpm=no'
 'build_alias=x86_64-redhat-linux-gnu'
 'host_alias=x86_64-redhat-linux-gnu' 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g
 -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
 -fstack-protector-strong --param=ssp-buffer-size=4
 -grecord-gcc-switches -m64 -mtune=generic' 'LDFLAGS=-Wl,-z,relro ''

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t

Recent input:
M-x r e p o r t - e m a c s - b u g <return>

Recent messages:
Loading /usr/share/emacs/site-lisp/site-start.d/desktop-entry-mode-init.el
(source)...done
Loading /usr/share/emacs/site-lisp/site-start.d/rpmdev-init.el (source)...done
Loading /usr/share/emacs/site-lisp/site-start.d/systemtap-init.el
(source)...done
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message cl-macs gv format-spec
rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils actionscript-mode cl cl-lib
time-date tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
lisp-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer loaddefs button faces cus-face macroexp files text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process dbusbind
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty emacs)