synaptic Segmentation Fault on Ubuntu 17.10

[Usamm]

Shortly after upgrading Ubuntu from 17.04 to 17.10, Synaptic stopped working, with "Segmentation Fault" on start.
Both the symptoms and the workaround are the same as in https://bugs.launchpad.net/synapse-project/+bug/1592008

This works:
sudo synaptic --display=:0

As it does appending ` --display=:0` to the end of `Exec=synaptic-pkexec` in the file `/usr/share/applications/synaptic.desktop`.

$ ls -l /tmp/.X11-unix
total 0
srwxr-xr-x 1 crusaderky homeusers 0 Nov 4 09:52 X0
srwxrwxr-x 1 gdm gdm 0 Nov 4 09:52 X1024

where crusaderky:homeusers is the user I'm logged in as.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: synaptic 0.84.2 [modified: usr/share/applications/synaptic.desktop]
ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
Uname: Linux 4.13.0-16-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.1
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Nov 4 10:10:55 2017
InstallationDate: Installed on 2015-12-02 (702 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: synaptic
UpgradeStatus: Upgraded to artful on 2017-10-22 (12 days ago)

[Launchpad Janitor (janitor)]

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

[Devon (devonfyson)]

Effects me on a fresh install. "synaptic --display=:0" didn't work but "xhost +local:" did as suggested in https://askubuntu.com/questions/614387/gksu-gtk-warning-cannot-open-display-0