The Travis build has been broken for 3 cycles: https://travis-ci.org/apache/calcite/builds
It occurs on the JDK11 JDOC=Y build, and started happening with https://gitbox.apache.org/repos/asf?p=calcite.git;a=commit;h=21fe666e9634ab9a752c7cc328924b68f6143afe. Vladimir, can you please take a look?
