Exception when missing namespace in CND file should have clearer message

Using the attached CND file, when calling CndImporter.registerNodeTypes(..) the following message is in the returned exception:

"Unable to parse CND Input: Error setting name of sling:resourceType to sling:resourceType (bundle://23.0:0/SLING-INF/nodetypes/types.cnd, line 24)"

The issue with line 24 is that the "sling" namespace has not been included. The message should state that a namespace is missing and what prefix is not understood.