On a Debian system, the working directory for bacula is /var/lib/bacula, but in https://github.com/netmanagers/puppet-bacula/blob/master/manifests/init.pp#L224 the default value is checked, which is /var/spool/bacula for all OS'es. Therefore,puppet tries to create this directory as a link, which fails as it was already installed with the package. The following error message is shown:
err: /Stage[main]/Bacula/File[/var/lib/bacula]/ensure: change from directory to link failed: Could not remove existing file
Providing a sane default for Debian systems would fix this issue.