bug#22649: 25.0.90; M-g doesn't work when Gnus is started with M-x gnus-no-server

[Daiki Ueno]

This is originally reported at:
http://article.gmane.org/gmane.emacs.gnus.general/85837
and Lars requested to file it here.

When I start Gnus with M-x gnus-no-server, hit M-g on some closed nnimap
group, I get the following backtrace:

--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (error "server/993 Name or service not known")
  make-network-process(:name "*nnimap*" :buffer #<buffer  *nnimap server nil  
*nntpd**> :host "server"
:service "993" :nowait nil)
  open-network-stream("*nnimap*" #<buffer  *nnimap server nil  *nntpd**> 
"server" "993")
  open-gnutls-stream("*nnimap*" #<buffer  *nnimap server nil  *nntpd**> 
"server" "993")
  ...
  nnimap-open-connection-1(#<buffer  *nntpd*>)
  nnimap-open-connection(#<buffer  *nntpd*>)
  nnimap-open-server("server" nil nil)
  nnimap-change-group(nil "server")
  nnimap-request-group-scan("INBOX" "server" ...)
  gnus-request-group-scan("nnimap+server:INBOX" ...)
  gnus-group-get-new-news-this-group(nil)
--8<---------------cut here---------------end--------------->8---

It used to work until the recent nnimap rework around Jan 2015.
Apparently newly added `nnimap-request-group-scan' called before
`gnus-activate-group' is causing the problem.

Here is some analysis:
http://article.gmane.org/gmane.emacs.gnus.general/86808

and the current proposed patch:
http://article.gmane.org/gmane.emacs.gnus.general/86824

In GNU Emacs 25.0.90.1 (x86_64-pc-linux-gnu, GTK+ Version 3.18.6)
 of 2016-02-07 built on debian
Repository revision: 9dc77e37aa84c6df9b3ddb4609f3c09201b0580e
Windowing system distributor 'The X.Org Foundation', version 11.0.11703000
System Description:     Debian GNU/Linux unstable (sid)

Configured using:
 'configure --with-x-toolkit=gtk3'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GCONF GSETTINGS NOTIFY ACL
LIBSELINUX GNUTLS LIBXML2 FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Group

Minor modes in effect:
  gnus-topic-mode: t
  cursor-sensor-mode: t
  gnus-undo-mode: t
  which-function-mode: t
  recentf-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
  blink-cursor-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

Recent messages:
Opening connection to mail.corp.redhat.com via tls...
Unable to open server nnimap+redhat due to: mail.corp.redhat.com/993 Name or 
service not known
Type C-x 1 to delete the help window, C-M-v to scroll help.
Reading active file via nnnil...done
nnimap read 0k from well-done.deisui.org (initial sync of 2 groups; please wait)
nnimap read 77k from well-done.deisui.org (initial sync of 2 groups; please 
wait)
Reading active file from archive via nnfolder...done
Reading active file via nndraft...done
Checking new news...done
Warning: Unable to open server nnimap+redhat due to: mail.corp.redhat.com/993 
Name or service not known

Load-path shadows:
None found.

Features:
(shadow sort gnus-cite mail-extr gnus-topic cursor-sensor nndraft nnmh
utf-7 plstore network-stream nsm auth-source cl-seq eieio byte-opt
bytecomp byte-compile cl-extra cconv eieio-core cl-macs gv starttls
nnfolder nnnil gnus-agent gnus-srvr gnus-score score-mode nnvirtual
gnus-msg gnus-art mm-uu mml2015 mm-view mml-smime smime password-cache
dig mailcap nntp gnus-cache nnir gnus-sum gnus-group gnus-undo
gnus-start gnus-cloud nnimap nnmail mail-source tls gnutls utf7 netrc
nnoo parse-time gnus-spec gnus-int gnus-range gnus-win gnus gnus-ems
nnheader emacsbug message dired format-spec rfc822 mml mml-sec epg
gnus-util mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
help-fns help-mode mail-prsvr mail-utils which-func imenu recentf
tree-widget wid-edit cl-loaddefs pcase cl-lib cus-start cus-load
finder-inf info package easymenu epg-config time-date mule-util tooltip
eldoc electric uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core 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 charscript case-table epa-hook jka-cmpr-hook help
simple abbrev 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 dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 344438 23264)
 (symbols 48 31388 0)
 (miscs 40 61 209)
 (strings 32 47598 7241)
 (string-bytes 1 1531231)
 (vectors 16 24662)
 (vector-slots 8 572449 8356)
 (floats 8 380 478)
 (intervals 56 1045 0)
 (buffers 976 20)
 (heap 1024 67600 1664))