It is obvious in retrospect, but not all providers will support ALL attributes for a given resource type.
Remember, the resource type can be universal, but how it’s managed on an individual host is controlled by an platform specific provider.
In the example given, the useradd provider manages adding a user in Linux, while the hp-ux provider manages adding the same user in HP-UX.
Evidently, the hp-ux provider does not have the ability to set the new user’s password. (I don’t have access to a HP-UX server right now to verify this, so we’ll just trust the book.) =)
This will not break the Puppet run, you’ll just get a warning that the attribute isn’t supported by the provider.