Comment 2 for bug 1477175

I had the same error. After reading the "ssh.py", I've seen it occured when there is no address associated with the host when ansible list host with inventory.

Ansible uses your inventory script with the argument "--host ubuntu2" and if there is something like that :

"{
    "ansible_ssh_host": null,
    "ansible_ssh_port": "22",
    "ansible_ssh_user": "username",
    "ansible_ssh_private_key_file": "~/.ssh/id_rsa"
}"

you can see "ansible_ssh_host" is null.

Hope it helps...