Type: fix
Since CentOS 8, RPM build script doesn't accept '#!/usr/bin/env python'
as a valid shebang line. It requires scripts to explicitly chose
between python2 or python3.
Change all to use python3 as suggested by Paul Vinciguerra.
Depends-On: https://gerrit.fd.io/r/23170
Signed-off-by: Renato Botelho do Couto <renato@netgate.com>
Change-Id: Ie72af9f60fd0609e07f05b70f8d96e738b2754d1
