Pretty it up a bit, maybe faster?

Also, axe the debug output.
3 jobs for master in 11 seconds
Name Stage Failure
lets-encrypt Deploy
Running with gitlab-runner 10.8.0 (079aad9e)
on b897c2bb
Using Docker executor with image certbot/certbot-dns-rfc2136 ...
Pulling docker image certbot/certbot-dns-rfc2136 ...
ERROR: Job failed: Error response from daemon: repository certbot/certbot-dns-rfc2136 not found: does not exist or no pull access