### What needs to get done Right now the workflow when reading a multi-document yaml file returns an internal error: ``` $ charmcraft pack charmcraft internal error: ComposerError('expected a single document in the stream', <yaml.error.Mark object at 0x73a1c3d77970>, 'but found another document', <yaml.error.Mark object at 0x73a1c3ce0340>) Full execution log: '/home/lengau/.local/state/charmcraft/log/charmcraft-20240920-152105.956862.log' ``` This should be converted to an error message that we don't support multi-document YAML files. ### Why it needs to get done Strange ux. See: https://github.com/canonical/charmcraft/issues/214