Ubuntu 17.10 beta installed on 6.10.2017: Still the same problem, not only with synaptic but also octave wouldn't work properly, gave similar error.
Solution was, as posted by dino99 to type: xhost +si:localuser:root.
Ubuntu 17.10 beta installed on 6.10.2017:
Still the same problem, not only with synaptic but also octave wouldn't work properly, gave similar error.
Solution was, as posted by dino99 to type: xhost +si:localuser:root.