function extractHookOutputFromResult(res) {
  return res.output
    .trim()
    .split('\n')
    .filter(function (line) {
      // every line that begins with whitespace (e.g., the test name) should be ignored;
      // we just want the console.log messages
      return /^\S/.test(line);
    })
    .sort();
}
Extracts root hook log messages from run results
`root-hook-defs-*` fixtures are root hook plugins which call `console.log()`
for verification that they have been run.
@param {RawResult} res - result of invokeMochaAsync()