traefik: Traefix does not start when LetsEncrypt does not work

Today we have suffered an issue when we tried to move our traefik tasks from one node to another. The scheduler has tried to launch the service in another node but it failed because of Letsencrypt failures.

$ docker inspect 9lb8xxxxxx (traefik task)
...
"Status": {
            "Timestamp": "2016-10-31T13:11:04.538031123Z",
            "State": "failed",
            "Message": "started",
            "Err": "task: non-zero exit (1)",
            "ContainerStatus": {
                "ContainerID": "b86862bdc9563a440c36861d4756055b1e26e4a0b08146bd00793c87d0d95b84",
                "ExitCode": 1
            }
        },
...
$ docker logs 551fc96db70c
time="2016-10-31T13:03:44Z" level=error msg="Error creating TLS config get directory at 'https://acme-v01.api.letsencrypt.org/directory': acme: Error 502 - urn:acme:error:serverInternal - The service is down for maintenance or had an internal error. Check https://letsencrypt.status.io/ for more details."
time="2016-10-31T13:03:44Z" level=fatal msg="Error preparing server: get directory at 'https://acme-v01.api.letsencrypt.org/directory': acme: Error 502 - urn:acme:error:serverInternal - The service is down for maintenance or had an internal error. Check https://letsencrypt.status.io/ for more details."

And it was because of a failure in Letsencrypt.

It provoked a downtime on our proxied services. But even our system at the moment didn’t need to generate any TLS certificate traefik failed its starting process.

Could this error be transformed to a warning or let the traefik server run when the Letsencrypt service is not working? As I said we didn’t need any new TLS certificate, because all of them were stored in a shared volume in our cluster. In this case the consequence is that even the services exposed in the 80 port were not working.