Executing commands through sudo or equivalent doesn't work

[Gilles Gravier]

Any application that needs to run with elevated privileges fails to launch on artful (17.10) desktop.

Whether it's run from a terminal with sudo (e.g. "sudo gnome-terminal") or directly from the GUI icon by clicking on the application itself (e.g. launch "Synaptic Package Manager" from the application list and then enter your password) the same behavior happens: Application does not run.

If doing this from a terminal, the resulting error message is:
  Unable to init server: Could not connect: Connection refused
  Failed to parse arguments: Cannot open display:

As a workaround, running "xhost +" from a terminal before allows all elevated privileges apps to now run. But this isn't helping apps that need to run at start of graphical environment and for which opening a terminal manually before to type "xhost +" isn't feasible.

This is a regression since 17.04.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.