MultipleSingletonsError reports that multiple singletons are defined in the same directory.

UnsyncableResourcesInLeaf reports that a leaf node has resources but is not a Namespace.

UnsyncableResourcesInNonLeaf reports that a node has resources and descendants, but none of its descendants are Namespaces.

MultipleSingletonsErrorCode is the error code for MultipleSingletonsError.

UnsyncableResourcesErrorCode is the error code for UnsyncableResourcesError.