bug#35300: 27.0.50; emacsclient on remote sessions no longer works

[Óscar Fuentes]

After initiating my KDE desktop session on the local machine, I also
execute emacs --daemon.

On the local machine `emacsclient -c'.

Now, if I ssh into my machine, `emacsclient -c -nw' shows:

emacsclient: can't find socket; have you started the server?
emacsclient: To start the server in Emacs, type "M-x server-start".
emacsclient: No socket or alternate editor.  Please use:

        --socket-name
        --server-file      (or environment variable EMACS_SERVER_FILE)
        --alternate-editor (or environment variable ALTERNATE_EDITOR)

I looked into NEWS and it has a few lines describing some changes but it
is not more useful than the above text about what I need to do to get a
working emacsclient.

(Saying "To get the old, less-secure behavior, you can set the
EMACS_SOCKET_NAME environment variable to an appropriate value." is not
helpful at all, it assumes that the user knows things that previously he
wasn't required to know.)


In GNU Emacs 27.0.50 (build 4, x86_64-pc-linux-gnu, X toolkit)
 of 2019-04-14 built on sky
Repository revision: 4fb1a06413224424bc7d022192c2434232dc5e9c
Repository branch: fill_column_indicator
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: Debian GNU/Linux buster/sid

Configured using:
 'configure --without-toolkit-scroll-bars --with-x-toolkit=lucid
 --with-modules'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG SOUND GSETTINGS GLIB NOTIFY INOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB LUCID X11 XDBE XIM
MODULES THREADS PDUMPER GMP

Important settings:
  value of $LANG: C
  locale-coding-system: nil