constructor() {
    Fail`Turn Exo JS classes into Exo classes with defineExoClassFromJSClass: ${q(
      new.target.name,
    )}`;
  }
Based on the WobblyPoint inheritance examples in
https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/google-caja/caja-spec-2007-12-21.pdf
and
test-far-wobbly-point.js