Could you not use the ```command_execution``` bundle to do this check? It returns the classes you need, and will return failed if the command does not return zero.

To clarify: the kept/failed classes are set according to attributes in the ```body classes``` used, which in this case is not set. From the CFEngine docs:

> If none of the attributes kept_returncodes, repaired_returncodes, or failed_returncodes are set, the default is to consider a return code zero as promise repaired, and nonzero as promise failed.

Using our  ```command_execution``` bundle would help to keep these bundles DRY, and ensure any bug workarounds implemented there also help this bundle.