Ansible Variables all of a Sudden Go Missing?

I’ve written a playbook which deploys a working development environment for some of our internal systems. I’ve tested it with various versions of RHEL. Yet when I ran it against a fresh install of Fedora it failed:

fatal: [192.168.1.233] => {'msg': "One or more undefined variables: 'ansible_lsb' is undefined", 'failed': True}

It turned out, that ansible gets it’s facts through different programs on the remote machine. If some of these programs are not available (in this instance it was lsb_release) the variables are not populated resulting in this error.

So check if all variables you access are indeed available with:

$ ansible -m setup <yourhost>