Add python3-compat boilerplate to all .py files in lib/ansible

lib/ansible/cli/playbook.py

@@ -18,6 +18,10 @@
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
 
 ########################################################
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
 import os
 import stat