private Map<String, Object> getKerberosDescriptor(String stackName, String stackVersion, String serviceName)
      throws NoSuchParentResourceException, IOException {

      return serviceName == null ?
          buildStackDescriptor(stackName, stackVersion) :
          getServiceDescriptor(stackName, stackVersion, serviceName);
  }
Get a kerberos descriptor.

@param stackName     stack name
@param stackVersion  stack version
@param serviceName   service name

@return map of kerberos descriptor data or null if no descriptor exists

@throws IOException if unable to parse the associated kerberos descriptor file
@throws NoSuchParentResourceException if the parent stack or stack service doesn't exist
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/StackArtifactResourceProvider.java