bep is referring to a superfluous warning that we recently removed.
In your case, given this front matter in a .pdc file:
---
title: Post 1
lang: fr
---
Hugo emits this warning:
WARN deprecated: lang in front matter was deprecated in Hugo v0.144.0 and will be removed in a future release.
We emit a similar warning if you specify kind or path in front matter. We will continue to warn until approximately v0.159.0 at which point we will throw an error. More about deprecation here.
To pass a lang attribute when running the pandoc exec, you need to do this:
I understand that solution, however, Pandoc understands lang in the front matter out of the box with no additional configuration files… along with other options.
I do not think that lang should throw an error. That seams unessesary.