message: improved error reporting in test suite
diff: let chai = require('chai');
  global.expect = chai.expect;
  chai.use(require('chai-things'));
  +
  +// Without this, we can't see stack traces for certain failures within
  +// promises during the test suite.
  +process.on('warning', (warning) => {
  + /* eslint-disable no-console */
  + console.warn(warning.stack);
  + /* eslint-enable no-console */
  +});
  