bug#27029: 26.0.50; gnus & utf are suddenly broken

[Sam Steingold <sds@gnu.org>]

I pulled emacs from git and now gnus cannot show utf8 characters.
In the *Summary* buffer, I see things like "=?utf-8?q?common=3f?=".
When I try to view such an article, I see:

--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (wrong-type-argument characterp ("utf-8" 113 "common=3f" "=?utf-8?q?common=3f?="))
  rfc2047-decode-encoded-words((("utf-8" 113 "common=3f" "=?utf-8?q?common=3f?=")))
  mail-decode-encoded-word-region(121 197)
  article-decode-encoded-words()
  run-hooks(gnus-article-decode-hook)
  gnus-request-article-this-buffer(63735 "nntp+news.gwene.org:gwene.com.reddit.r.jokes")
--8<---------------cut here---------------end--------------->8---

the only change is git pull and rebuild.
the previous time I rebuilt emacs was 



In GNU Emacs 26.0.50 (build 6, x86_64-apple-darwin16.6.0, NS appkit-1504.83 Version 10.12.5 (Build 16F73))
 of 2017-05-22 built on Clr-Sam.local
Repository revision: 62046ed3e9b1e95340eb980058b8f7aadae2447a
Windowing system distributor 'Apple', version 10.3.1504
Recent messages:

Mark saved where search started
Truncate long lines disabled
Exiting summary buffer and applying spam rules
Truncate long lines disabled
mail-decode-encoded-word-region: Wrong type argument: characterp, ("utf-8" 113 "Europe\"=3f" "=?utf-8?q?Europe\"=3f?=")
Quit
funcall-interactively: No recursive edit is in progress [7 times]
Truncate long lines disabled
Entering debugger...
Back to top level

Configured using:
 'configure --with-mailutils --with-ns
 PKG_CONFIG_PATH=/usr/local/opt/libxml2/lib/pkgconfig:/usr/local/opt/imagemagick/lib/pkgconfig/
 --without-makeinfo'

Configured features:
JPEG NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LANG: C
  locale-coding-system: utf-8-unix

Major mode: VC dir

Minor modes in effect:
  vc-parent-buffer: *vc-dir*<trunk>
  pyvenv-mode: t
  shell-dirtrack-mode: t
  rcirc-track-minor-mode: t
  diff-auto-refine-mode: t
  which-function-mode: t
  url-handler-mode: t
  show-paren-mode: t
  desktop-save-mode: t
  cl-old-struct-compat-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-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
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t

Load-path shadows:
/Users/sds/.emacs.d/elpa/scala-mode-20161122.2325/ob-scala hides /Users/sds/src/emacs/trunk/lisp/org/ob-scala

Features:
(shadow sort gnus-cite bbdb-message mailalias cookie1 nnir emacsbug
sendmail debug gnus-bcklg qp gnus-async gnus-dup mail-extr gnus-ml
hl-line disp-table man tabify spam spam-stat gnus-uu yenc nndraft nnmh
gnus-agent gnus-srvr gnus-score score-mode nnvirtual gnus-msg gnus-art
mm-uu mml2015 mm-view mml-smime smime dig utf-7 gnus-cache gnus-sum
bbdb-gnus network-stream nsm starttls nntp gnus-group gnus-undo
tramp-cmds gnus-start gnus-cloud nnimap nnmail mail-source tls gnutls
utf7 netrc nnoo gnus-spec gnus-int gnus-range gnus-win log-edit message
subr-x rfc822 mml mml-sec epa epg epg-config mm-decode mm-bodies
mm-encode mail-parse rfc2231 gmm-utils mailheader smerge-mode dabbrev
skeleton eieio-opt speedbar sb-image ezimage dframe find-func cl-indent
pp cl-print log-view pcvs-util misearch multi-isearch noutline outline
tramp-cache add-log remember conf-mode view 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 nxml-util
nxml-enc xmltok arc-mode archive-mode cursor-sensor mhtml-mode css-mode
smie color eww puny mm-url url-queue url url-proxy url-privacy
url-expand url-methods url-history url-cookie url-domsuf url-util
mailcap shr svg xml browse-url js sgml-mode dom dired-aux dired
dired-loaddefs d-mode cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs make-mode vc-hg flyspell
ispell company-oddmuse company-keywords company-etags company-gtags
company-dabbrev-code company-dabbrev company-files company-cmake
company-xcode company-clang company-eclim company-template company-css
company-nxml company-bbdb cl-extra yasnippet flymake company help-fns
radix-tree help-mode elpy find-file-in-project ivy delsel ivy-overlay
ffap thingatpt pyvenv elpy-profile elpy-django s elpy-refactor derived
edmacro kmacro ido grep compile files-x etags xref project cus-edit
python tramp-sh tramp tramp-compat tramp-loaddefs trampver shell
pcomplete parse-time format-spec advice json comint ansi-color rcirc
ring vc-git diff-mode easy-mmode map vc-dir ewoc vc vc-dispatcher
finder-inf info package seq warnings midnight ein-loaddefs gnus nnheader
gnus-util rmail rmail-loaddefs rfc2047 rfc2045 ietf-drums mail-utils
mm-util mail-prsvr wid-edit bbdb-mua bbdb-com crm mailabbrev
bbdb-loaddefs bbdb easymenu bbdb-site timezone server which-func imenu
url-handlers url-parse auth-source cl-seq eieio byte-opt bytecomp
byte-compile cconv eieio-core cl-macs eieio-loaddefs password-cache
url-vars paren help-at-pt desktop frameset cus-start cus-load cl gv
cl-loaddefs pcase cl-lib time-date tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win 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 kqueue cocoa ns multi-tty make-network-process emacs)

Memory information:
((conses 16 1063555 91570)
 (symbols 48 51869 36)
 (miscs 40 23457 906)
 (strings 32 246544 12089)
 (string-bytes 1 6101843)
 (vectors 16 98839)
 (vector-slots 8 1782849 31048)
 (floats 8 520 1052)
 (intervals 56 53716 327)
 (buffers 976 134))

-- 
Sam Steingold (http://sds.podval.org/) on darwin Ns 10.3.1504
http://steingoldpsychology.com http://www.childpsy.net http://camera.org
https://ffii.org http://thereligionofpeace.com http://americancensorship.org
If money were measured in piles, I would have had a pit of it.