Replacing existing certbot-auto installation on Ubuntu 14 with Docker
The problem: Legacy certbot-auto is no longer supported, and ACMEv1 challenge has been
deprecated and removed. On newer systems, you can simply upgrade certbot using
apt-get install --upgrade-only certbot and you'll be good to go.
However, on legacy servers (Ubuntu 14), it isn't possible to upgrade. Installing manually isn't good
python3 uses python3.4 which has a broken pip installation (ugh).
Docker to the rescue!