bug#31267: 27.0.50; Calendar with documented value for 'calendar-date-echo-text fails

[Brian Carlson <hacker@abutilize.com>]

Tried to use M-x calendar with calendar-date-echo-text set (exactly as
documented):

Reproduction:
  $ emacs -Q
 
  (setq calendar-date-echo-text '(format "ISO date: %s"
                                         (calendar-iso-date-string
                                          (list month day year))))
  M-x calendar
      => calendar-iso-date-string: Symbol’s value as variable is void: month

 
                                         





In GNU Emacs 27.0.50 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2018-04-25 built on lgw01-amd64-037
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description: Ubuntu 16.04.4 LTS

Recent messages:
Type C-x 1 to delete the help window, C-M-v to scroll help.
Mark set [2 times]
Undo!
(format "ISO date: %s" (calendar-iso-date-string (list month day year)))
next-line: End of buffer
C-x C-g is undefined
Undo!
Mark set [2 times]
calendar-iso-date-string: Symbol’s value as variable is void: month
Scanning for dabbrevs...done

Configured using:
 'configure --build=x86_64-linux-gnu --prefix=/usr
 '--includedir=${prefix}/include' '--mandir=${prefix}/share/man'
 '--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var
 --disable-silent-rules '--libdir=${prefix}/lib/x86_64-linux-gnu'
 '--libexecdir=${prefix}/lib/x86_64-linux-gnu' --disable-maintainer-mode
 --disable-dependency-tracking --prefix=/usr --sharedstatedir=/var/lib
 --program-suffix=-snapshot --with-modules=yes --with-x=yes
 --with-x-toolkit=gtk3 --with-xwidgets=yes 'CFLAGS=-g -O2
 -fstack-protector-strong -Wformat -Werror=format-security'
 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2'
 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES THREADS XWIDGETS LIBSYSTEMD LCMS2

Important settings:
  value of $LC_COLLATE: C
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: Calendar

Minor modes in effect:
  diff-auto-refine-mode: t
  tooltip-mode: t
  global-eldoc-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
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/usr/share/emacs/site-lisp/dictionaries-common/ispell hides /usr/share/emacs/27.0.50/lisp/textmodes/ispell
/usr/share/emacs/site-lisp/dictionaries-common/flyspell hides /usr/share/emacs/27.0.50/lisp/textmodes/flyspell

Features:
(shadow sort mail-extr dabbrev emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv format-spec rfc822 mml mml-sec
password-cache epa derived epg epg-config gnus-util rmail rmail-loaddefs
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils cal-iso cl-print cal-coptic cal-julian cal-move cal-x
holidays hol-loaddefs solar cal-dst cal-menu calendar cal-loaddefs
thingatpt help-fns radix-tree help-mode cl-loaddefs cl-lib misearch
multi-isearch vc-git diff-mode easymenu easy-mmode dired dired-loaddefs
time-date elec-pair mule-util tooltip eldoc electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow isearch timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core term/tty-colors frame 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 charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting xwidget-internal
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 118765 9254)
 (symbols 48 21449 1)
 (miscs 40 94 201)
 (strings 32 34604 2534)
 (string-bytes 1 931661)
 (vectors 16 15980)
 (vector-slots 8 513191 14068)
 (floats 8 407 128)
 (intervals 56 910 24)
 (buffers 992 16)
 (heap 1024 47756 1329))