There are two big reasons for doing so:
  - It relied on functions that were internal to ansible and whole behavior has now changed.
    The functions to get the extensions and filters from ansible can still be accessed after
    instantiating an object of the Templar class but the way that this loads variables has
    now changed and so we can't do the same sort of tests as we did previously without loading
    the entire variable context for the template file.
  - This test should now be achieved by running the relevant docker builds that test the templates
    can render correctly within the full context they need.

To catch errors faster we may want to add a jinja linter that does the rudimentry syntax checks
without needing to know about the ansible jinja filters and extensions that are available.