https://travis-ci.com/saltstack-formulas/syslog-ng-formula/builds/129135816#L210-L217:

```bash
$ yamllint -s .
./test/salt/pillar/syslog_ng.sls
  4:24      warning  truthy value should be one of [false, true]  (truthy)
  6:16      warning  truthy value should be one of [false, true]  (truthy)
  7:17      warning  truthy value should be one of [false, true]  (truthy)
  16:7      error    wrong indentation: expected 8 but found 6  (indentation)
  20:7      error    wrong indentation: expected 8 but found 6  (indentation)
  25:7      error    wrong indentation: expected 8 but found 6  (indentation)
```