sudo in X-environment

[Johann Spies <johann.spies@gmail.com>]

For years I have used sudo both in server administration and on the desktop.

Lately I get the following error message and I do not really know what 
to do about it other than logging into the xserver as root - which I do 
not want to do:

$ sudo system-config-printer

No protocol specified
error: XDG_RUNTIME_DIR not set in the environment.
Unable to init server: Could not connect: Connection refused
No protocol specified

** (system-config-printer.py:5632): WARNING **: Could not open X display
No protocol specified
error: XDG_RUNTIME_DIR not set in the environment.
Unable to init server: Could not connect: Connection refused
No protocol specified
error: XDG_RUNTIME_DIR not set in the environment.
Unable to init server: Could not connect: Connection refused

Why is it now a problem while previously I had no hassles?

How do I solve it?

3.10-2-amd64 #1 SMP Debian 3.10.7-1 (2013-08-17) x86_64 GNU/Linux

Regards
Johann

--
J.H. Spies - Tel. 021-982 2694 / 082 782 0336 / 021-808 4699(w)
             Posbus 4668, Tygervallei 7536

     "Submit yourselves therefore to God. Resist the devil,
      and he will flee from you."          James 4:7