Better error message: "Error: Playbook file does not exist."
As a user, I would like for the error message when the playbook file is not found to tell me where antora is looking for the file. For example: "Error: Playbook file does not exist at user/projects/docs/antora-playbook.yml"
This is helpful when using Docker, build servers, and other times where you're creating and/or manipulating directories.