Fixes the problem in #35 (comment)
/cc @tobias-urdin - The fix was actually pretty easy (e3531b3) and then I added a bunch of testing around it. Could you try this branch and see if the issue you reported is fixed?
Add test for hiera config in the environment
Enable specified environments for hiera configuration, un-hardcode pr…
Add unit tests around hiera setup in alternate environments
@kpaulisse I can confirm that this change solves the problem, I can now successfully compile and diff using hiera data for environments.