/etc/apt/preferences

Package: *
Pin: release n=jessie
Pin-Priority: 900

Package: *
Pin: release n=jessie-backports
Pin-Priority: 700

# Architecture independent packages
Package: python-pkg-resources python-configargparse python-six python-idna python-ipaddress python-pyasn1 python-setuptools python-dnspython python-funcsigs python-openssl python-ndg-httpsclient python-pbr python-urllib3 python-requests python-rfc3339 python-mock python-acme python-certbot certbot
Pin: release n=jessie-backports
Pin-Priority: 995

Package: *
Pin: release o=Raspbian
Pin-Priority: -10