bug#54993: 28.1; Editing etc/NEWS on master with Emacs 28 signals an error

[Eli Zaretskii <eliz@gnu.org>]

  emacs -Q
  C-x C-f etc/NEWS RET

Observe an error message:

  File local-variables error: (void-function emacs-news-mode)

and NEWS is visited in Fundamental mode, which makes it annoyingly
inconvenient to edit the news entries.

I think a new mode that is only available in the development version
should not be forced on all the developers, because not all of them
use the latest-and-the-greatest code all the time while working on
Emacs.

Please make it possible to edit NEWS conveniently with older versions
of Emacs.


In GNU Emacs 28.1 (build 2, i686-pc-mingw32)
 of 2022-04-03 built on HOME-C4E4A596F7
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
System Description: Microsoft Windows XP Service Pack 3 (v5.1.0.2600)

Configured using:
 'configure --prefix=/d/usr --with-wide-int --with-native-compilation
 'CFLAGS=-O2 -gdwarf-4 -g3''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES
NATIVE_COMP NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF
TOOLKIT_SCROLL_BARS XPM ZLIB

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Mail

Minor modes in effect:
  shell-dirtrack-mode: t
  flyspell-mode: t
  desktop-save-mode: t
  save-place-mode: t
  display-battery-mode: t
  display-time-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-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
  temp-buffer-resize-mode: t
  line-number-mode: t
  auto-fill-function: mail-mode-auto-fill
  indent-tabs-mode: t
  abbrev-mode: t

Load-path shadows:
d:/usr/share/emacs/site-lisp/soap-client hides d:/usr/share/emacs/28.1/lisp/net/soap-client

Features:
(shadow emacsbug quail lao-util enriched smerge-mode diff calc-ext
calc calc-loaddefs rect calc-macs arc-mode archive-mode thai-util
thai-word pcase descr-text rng-xsd xsd-regexp rng-cmpct rng-nxml
rng-valid rng-loc rng-uri rng-parse nxml-parse rng-match rng-dt
rng-util rng-pttrn nxml-ns nxml-mode nxml-outln nxml-rap sgml-mode
nxml-util nxml-enc xmltok ede/speedbar ede/files ede ede/detect
ede/base ede/auto ede/source eieio-base eieio-speedbar eieio-custom
cedet edebug backtrace gud completion find-cmd grep find-dired
skeleton tabify autoconf autoconf-mode ffap ebuff-menu compile pulse
etags fileloop generator vc-mtn vc-hg vc-src vc-sccs vc-svn cl-print
thingatpt eieio-opt speedbar ezimage dframe find-func shortdoc
help-fns radix-tree sh-script smie executable texinfo texinfo-loaddefs
novice misearch multi-isearch dabbrev shr-color color rmailout shell
pcomplete comint ansi-color rfc2104 gnutls network-stream nsm
mail-extr smtpmail mailalias sendmail cc-awk jka-compr bat-mode
dired-aux vc-bzr generic noutline outline make-mode vc-cvs vc-rcs
conf-mode vc bug-reference add-log mule-util info vc-git diff-mode
easy-mmode vc-dispatcher flyspell rmailsum shr kinsoku svg dom
browse-url url url-proxy url-privacy url-expand url-methods
url-history url-cookie url-domsuf url-util url-parse url-vars mailcap
qp rmailmm message rmc puny rfc822 mml mml-sec epa epg rfc6068
epg-config gnus-util text-property-search time-date mm-decode
mm-bodies mm-encode mailabbrev gmm-utils mailheader mail-parse rfc2231
rmail rmail-loaddefs auth-source eieio eieio-core eieio-loaddefs
password-cache json map rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils desktop frameset server find-lisp dired dired-loaddefs
filecache mairix cus-edit pp cus-load wid-edit saveplace midnight
facemenu ispell derived generic-x cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs xref project ring
format-spec battery dbus xml time comp comp-cstr warnings subr-x rx
cl-seq cl-macs cl-extra help-mode seq byte-opt gv cl-loaddefs cl-lib
bytecomp byte-compile cconv iso-transl tooltip eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel dos-w32
ls-lisp disp-table term/w32-win w32-win w32-vars term/common-win
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode lisp-mode prog-mode register page tab-bar
menu-bar rfn-eshadow isearch easymenu timer select scroll-bar mouse
jit-lock font-lock syntax font-core term/tty-colors frame minibuffer
cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese composite
emoji-zwj charscript charprop case-table epa-hook jka-cmpr-hook help
simple abbrev obarray cl-preloaded nadvice button loaddefs faces
cus-face macroexp files window text-properties overlay sha1 md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote threads w32notify w32 lcms2 multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 3198865 323401)
 (symbols 48 43159 3)
 (strings 16 264038 30739)
 (string-bytes 1 8154768)
 (vectors 16 98734)
 (vector-slots 8 2868549 238198)
 (floats 8 365 538)
 (intervals 40 589593 24500)
 (buffers 888 317))