Unarchive module gets cert error on get.docker.com on Ubuntu 14.04 LTS. System Python is too old.
My dream would be that whole Ansible would use rockstable libcurl instead of the requests library which has problems with Certs on (not so) old python versions.
The issue is more basic than requests, the actual python http/url and ssl implementations have these issues, we have patched and added warnings to indicate which minimal python versions you can use and have SNI work.