bug#37221: 27.0.50; gnus fails to open connection post-NSM update

[Alex Branham]

Hi -

After the recent NSM update gnus fails to open my mail with this message:

Warning: Opening nnimap server on LocalMail...failed: ; Unable to open server 
nnimap+LocalMail due to: Buffer  *nnimap localhost nil  *nntpd** has no process

My setup is that I use mbsync/isync to download the mail and run dovecot
read the maildir and host it as an imap server. Since it's local it's
not encrypted. Setting network-security-protocol-checks to nil does not
change anything. I've only recently started using dovecot/gnus so it's
possible I've done something silly but it was working before the NSM
update (at commit ef8531d262081d91ecf2a4f349bc63a0fede90d4) and isn't
working as of 4b87169d113a151e5d9d6cf7b0d7cb4fb1d3d2d7.

Thanks,
Alex

In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.10)
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: NixOS 19.03.173394.147bd882fc6 (Koi)

Recent messages:
Warning: Opening nnimap server on LocalMail...failed: ; Unable to open server 
nnimap+LocalMail due to: Buffer  *nnimap localhost nil  *nntpd** has no process
Saving file /home/alex/Sync/emacs/gnus/.newsrc-dribble...
Wrote /home/alex/Sync/emacs/gnus/.newsrc-dribble
(Saved .newsrc-dribble)
Mark set
Are you sure you want to quit reading news? (y or n) y
Saving /home/alex/Sync/emacs/gnus/.newsrc.eld...
Saving file /home/alex/Sync/emacs/gnus/.newsrc.eld...
Wrote /home/alex/Sync/emacs/gnus/.newsrc.eld
Saving /home/alex/Sync/emacs/gnus/.newsrc.eld...done

Configured using:
 'configure
 --prefix=/nix/store/7rfv0dv583css6s7drg71bj4p3gv77dj-emacs-27.0.50
 --disable-build-details --with-modules --with-x-toolkit=gtk3 --with-xft
 CFLAGS=-DMAC_OS_X_VERSION_MAX_ALLOWED=101200'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD JSON
PDUMPER GMP

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Memory information:
((conses 16 436220 242939)
 (symbols 48 42227 20)
 (strings 32 127301 28815)
 (string-bytes 1 4640702)
 (vectors 16 72982)
 (vector-slots 8 1109088 233166)
 (floats 8 581 295)
 (intervals 56 651 192)
 (buffers 992 24))