Minor Description
This should be more or less a one-line change: https://github.com/apache/incubator-reef/blob/master/lang/java/reef-tang/tang/src/main/java/org/apache/reef/tang/formats/ConfigurationModule.java#L250. It would seriously improve the usability of Tang's runtime checking of ConfigurationModule instantiations, since otherwise the user is left guessing which missing required parameter might be at fault.