If I’m reading the code correctly, certbot-auto currently uses python-cryptography version 1.3.4, which does not appear to support OpenSSL 1.1.0.
You’ll probably have to wait for that dependency to be updated. Not sure if that’s being worked on. I believe a number of popular projects are not quite compatible with OpenSSL 1.1.0 yet, so I guess sticking with the previous release branch for a while longer (at least system-wide; you could still compile your (web)server against that release, if it’s supported) would make your life a bit easier for now. 