On which server are you seeing these logs?

On puppet masters that use puppet 4.10.

https://puppet.com/docs/puppet/4.10/hiera_intro.html#i-use-a-custom-hiera-3-backend-can-i-use-hiera-5

Hmm i doin't see the warnning now.

And also this seems to be with puppet 4.10 https://groups.google.com/forum/#!topic/puppet-users/4bwJofklqyw

@Paladox can you add a specific host name where this happens? and paste the relevant lines from the log? Aren't these merely info level?

Here's the online docs for the conversion https://puppet.com/docs/puppet/4.10/hiera_migrate_v3_yaml.html