I recently came across this one as part of a PostgreSQL upgrade I run on my Linux (Debian) box.
Going from version PostgreSQL 9.4 to 9.5 worked like a charm. Upgrading to version 9.6 did not go as well though … The error I was getting was:
FATAL: could not load server certificate fileContinue reading “The snakeoil ssl certificate”
"/etc/ssl/certs/ssl-cert-snakeoil.pem": ee key too small