Small thing which may save some time wasting. On https://certbot.eff.org/docs/install.html page, Debian section still suggests use of Jessie backports. This is a bad idea and the https://certbot.eff.org/instructions page does indeed lead to the right answer, i.e. use certbot-auto. Suggest editing the install.html page.
Thanks @Callmebilly,
Thanks @Callmebilly for taking the time to point this out to us and @cpu for the ping.
I opened a PR to fix this at https://github.com/certbot/certbot/pull/7336.