Have you created any of the Hiera data files (common.yaml, site/*.yaml, etc.)? There does not appear to be a definition of which classes to include. If you change hiera_include('classes') to hiera_include('classes', []) the error message should go away (because [] provides a default empty array of classes); but you should also have something like this in your Hiera YAML files:
common.yaml: --- classes: - ntp > > -- You received this message because you are subscribed to the Google Groups "Puppet Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to puppet-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/puppet-users/fe5720a5-750a-487b-a42e-7c23ca19ad18%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.