print() is a function in Python 3

CLA: trivial

Discovered via #7410 @ https://travis-ci.org/openssl/openssl/jobs/442003489#L440



Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/7403)