Failing to install certbot on debian jessie

did you follow instructions above that to enable backports? You need to add

deb http://ftp.debian.org/debian jessie-backports main

to your /etc/apt/sources.list

Had the error message above. Running apt-get update (per the instructions) after adding the jessie-backports repository solved the problem for me

If you are using Digital Ocean, they replace the APT sources with their own mirror. You can add backports support by adding this to your /etc/apt/sources.list

deb http://mirrors.digitalocean.com/debian jessie-backports main
deb-src http://mirrors.digitalocean.com/debian jessie-backports main

Add this to your /etc/apt/source.list

deb http://mirrors.digitalocean.com/debian jessie-backports main
deb-src http://mirrors.digitalocean.com/debian jessie-backports main

run apt-get update after that run

sudo apt-get install python-certbot-apache -t stretch

simple change sudo stretch-backports to stretch