Let's Try Let's Encrypt

If you get this

gpg: keyring `/tmp/tmptwv64yji/secring.gpg' created
gpg: keyring `/tmp/tmptwv64yji/pubring.gpg' created
gpg: requesting key XXXXXXX from hkp server keyserver.ubuntu.com
gpgkeys: key YOURKEY can't be retrieved
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0
gpg: keyserver communications error: keyserver helper general error
gpg: keyserver communications error: unknown pubkey algorithm
gpg: keyserver receive failed: unknown pubkey algorithm
Failed to add key.

Try this

sudo apt-key adv --recv-key --keyserver keyserver.ubuntu.com YOURKEY

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/mybrailler.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/mybrailler.com/privkey.pem
   Your cert will expire on 2018-04-09. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot again
   with the "certonly" option. To non-interactively renew *all* of
   your certificates, run "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by: