Crash on invalid YAML file

[dflock]

If you point asible-review at this YAML file (or presumably any broken/invalid YAML file):

test: [one, two]
  three, four]

you get the error message form pyaml and ansible-review quits:

INFO: Playbook ./ansible/broken_yaml/broken_yaml_1.yml declares standards version 0.1
Failed to parse YAML in ./ansible/broken_yaml/broken_yaml_1.yml: while parsing a block mapping
  in "<unicode string>", line 1, column 1:
    test: [one, two]
    ^
expected <block end>, but found '<scalar>'
  in "<unicode string>", line 2, column 3:
      three, four]
      ^

Ansible-review should trap this error and emit an ERROR:... message, and continue.