You updated your packages recently, I imagine?
You need to stop Watchtower:
sudo docker stop watchtower
Supprimer le container :
sudo docker rm watchtower
Then run this version:
sudo docker run -d \\
--name watchtower \\
--restart=always \\
-v /var/run/docker.sock:/var/run/docker.sock \\
nickfedor/watchtower \\
--cleanup --include-restarting