exitMochaLater = clampedCode => {
  process.on('exit', () => {
    process.exitCode = Math.min(clampedCode, process.argv.includes('--posix-exit-codes') ? 1 : 255);
  });
}
Exits Mocha when tests + code under test has finished execution (default)
@param {number} clampedCode - Exit code; typically # of failures
@ignore
@private