The problem is on python-acme v0.10.2-1 … downgrading it to 0.9.3 should serve as a workaround as stated here https://community.letsencrypt.org/t/installing-certbot-on-debian-8-os-package-manager-not-installing-certbot/31194/6
apt-get remove python-acme
wget http://ftp.us.debian.org/debian/pool/main/p/python-acme/python-acme_0.9.3-1~bpo8+1_all.deb
dpkg -i python-acme_0.9.3-1~bpo8+1_all.deb
apt-get install certbot -t jessie-backports
apt-mark hold python-acme