Cause: API change in python-websockify
Consequence: engine-setup fails stopping ovirt-engine-websocket if python-websockify is upgraded before executing engine-setup. This can happen only if after enabling 3.6 user perform "yum update --skip-broken".
Workaround (if any):
avoid to run "yum update --skip-broken" and just execute "yum update rhevm-setup\*" and then engine-setup.
Result: it should work without further issue.