In recent versions of charmcraft (3.1.x), the prime
key was deprecated, meaning this way of placing files in charms is no longer valid and has to be changed in charms’ metadata.
The following note was added to the docs:
If your charm currently uses the
prime
key to include extra files: Note that, starting with Charmcraft 3.0, this key will become obsolete and you will see lint errors indicating that unknown additional files have been added. Users can still use this method to filter existing files.
The problem is that there is no suggestion for what to do instead. I think it would be helpful to add another set of instructions for 3.x to say what would be the replacement of this deprecated key. In my case, I did what this comment suggests and it worked.