Você pode usar puppet apply --help
para ver todas as opções disponíveis. Este é o que você está interessado:
* --detailed-exitcodes:
Provide transaction information via exit codes. If this is enabled, an exit
code of '2' means there were changes, an exit code of '4' means there were
failures during the transaction, and an exit code of '6' means there were both
changes and failures.
No seu caso específico:
# puppet apply --detailed-exitcodes --debug --modulepath modules manifests/host.pp