Occurs from this method https://github.com/apache/commons-rdf/blob/master/jena/src/main/java/org/apache/commons/rdf/jena/impl/JenaDatasetImpl.java#L152 on instantiation:
The exception message is "No dataset writer for N-Triples/utf-8".
The source is RDFWriterRegistry that builds a registryDataset HashMap of 17 RDFFormats that does not include this serialization. The registryGraph HashMap has 25 RDFFormats that does include "N-Triples/utf-8".
No exception is thrown if Lang.NQUADS is set in the toString() method.