X11vnc.service error after update

good day
this morning i tried to x11vnc into a newly um 18.04 installed machine.
i use a script to install x11vnc and create x11vnc.service.
this script has worked all through um 16.04 and up till to day with um 18.04.

my x11vnc.service file

[Unit]
Description="x11vnc"
Requires=display-manager.service
After=display-manager.service

[Service]
ExecStart=/usr/bin/x11vnc -xkb -noxrecord -noxfixes -noxdamage -auth /var/run/lightdm/root/:0 -auth guess -rfbauth /etc/x11vnc.pass
ExecStop=/usr/bin/killall x11vnc
Restart=on-failure
Restart-sec=15

[Install]
WantedBy=multi-user.target

error i'm getting when i try to start x11vnc.service cli

sudo systemctl daemon-reload
sudo systemctl enable x11vnc
sudo systemctl start x11vnc
systemctl status x11vnc.service

systemctl status x11vnc.service
‚óŹ x11vnc.service - "x11vnc"
Loaded: loaded (/etc/systemd/system/x11vnc.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Mon 2019-06-10 11:46:15 EDT; 4s ago
Process: 2566 ExecStart=/usr/bin/x11vnc -xkb -noxrecord -noxfixes -noxdamage -auth /var/run/lightdm/root/:0 -auth guess -rfbauth /etc/x11vnc.pass (code=exited, status=203/
Main PID: 2566 (code=exited, status=203/EXEC)

Jun 10 11:46:15 dc5700 systemd[1]: x11vnc.service: Service hold-off time over, scheduling restart.
Jun 10 11:46:15 dc5700 systemd[1]: x11vnc.service: Scheduled restart job, restart counter is at 5.
Jun 10 11:46:15 dc5700 systemd[1]: Stopped "x11vnc".
Jun 10 11:46:15 dc5700 systemd[1]: x11vnc.service: Start request repeated too quickly.
Jun 10 11:46:15 dc5700 systemd[1]: x11vnc.service: Failed with result 'exit-code'.
Jun 10 11:46:15 dc5700 systemd[1]: Failed to start "x11vnc".

i believe an update to systemd has changed something .
but have no idea where to start to fix it
after much googling i have tried
Restart-sec=2
to
Restart-sec=15
Restart-sec=2
to
Restartsec=2

Restart=on-failure
Restart-sec=15
to
#Restart=on-failure
#Restart-sec=15
all of that changes the errors to other errors but doesn't start x11vnc.service

well
my install script goofed
my install script :

x11vnc_set_up.sys(){
pathC=/etc/systemd/system/x11vnc.service
sudo apt-get install -y x11vnc
sudo apt-get install -y xtightvncviewer
cp /home/$USER/install_software/my-scripts/x11vnc.pass /etc/x11vnc.pass
chown root:root /etc/x11vnc.pass
touch $pathC
echo " [Unit]" >> $pathC
echo " Description="x11vnc" " >> $pathC
echo " Requires=display-manager.service" >> $pathC
echo " After=display-manager.service" >> $pathC
echo " " >> $pathC
echo " [Service]" >> $pathC
echo " ExecStart=/usr/bin/x11vnc -xkb -noxrecord -noxfixes -noxdamage -auth /var/run/lightdm/root/:0 -auth guess -rfbauth /etc/x11vnc.pass" >> $pathC
echo " ExecStop=/usr/bin/killall x11vnc" >> $pathC
echo " Restart=on-failure" >> $pathC
echo " Restart-sec=2" >> $pathC
echo " " >> $pathC
echo " [Install]" >> $pathC
echo " WantedBy=multi-user.target" >> $pathC
chown root:root /etc/systemd/system/x11vnc.service
chmod 700 /etc/systemd/system/x11vnc.service
systemctl daemon-reload
systemctl enable x11vnc
systemctl start x11vnc
}

only it did not install x11vnc after installing x11vnc it works as expected