In playbooks, hosts can be a YAML list. We templated the list before
converting it to a semicolon-separated string, which actually templated its
repr. This converts to a string first. A basic unit test is included.
Playbook test for no vars_files with len(), but that excepts if play.vars_files==None, as can happen when there's a vars_files section with no vars files listed. What is the ansible way: ignore, warn, or fail with message (instead of traceback)?
