Comment 2 for bug 1690432

From the journal errors:

ماي 12 19:13:47 hostname org.gtk.vfs.Daemon[1646]: ** (gvfsd:1724): WARNING **: dbus_mount_reply: Error from org.gtk.vfs.Mountable.mount(): Failed to retrieve share list from server: Connection refused
ماي 12 19:13:47 hostname org.gtk.vfs.Daemon[1646]: ** (process:5169): WARNING **: Couldn't create directory monitor on smb://x-gnome-default-workgroup/. Error: The specified location is not mounted
...
ماي 12 19:32:00 hostname com.ubuntu.OneConf[1646]: WARNING:oneconf.hosts:Error in loading other_hosts file: [Errno 2] No such file or directory: '/home/overdoz/.cache/oneconf/96c88f9cc88d498f726b551d58eabcdd/other_hosts'

So it looks like the system is set up to use oneconf, but couldn't communicate with the service for some reason. Later on, postfix attempts to make a system conf change, to add the postgres user to the ssl-cert group, and then fails:

Setting up postgresql-common (173) ...
Adding user postgres to group ssl-cert
dpkg: error processing package postgresql-common (--configure):
 subprocess installed post-installation script returned error exit status 10

Looking in postgres' postinst, the config code is attempting to add the user to the group here:

    # Add postgres user to the ssl-cert group on fresh installs
    if [ -z "$2" ]; then
        if getent group ssl-cert >/dev/null; then
            adduser $quiet postgres ssl-cert
        fi
    fi