write-inventory: add ansible_python_interpreter variable

This is also a variable which may be important to copy over to
a new inventory in order for ansible to function correctly.

Change-Id: I7f4f1b2c631a4a02c258c9f518cd19511fa118da

roles/write-inventory/library/write_inventory.py

@@ -20,6 +20,7 @@ from ansible.module_utils.basic import AnsibleModule
 
 # The list of variables we might include
 VARS = [
+    'ansible_python_interpreter',
     'ansible_connection',
     'ansible_host',
     'ansible_port',