if (args.length === 1 && args[0] instanceof Error) {
    var err = args[0];
    console.error('Error: "' + err.message + '".  Stack:\n' + err.stack);
  }
Small utility that can be used as an error handler. You cannot just pass
`console.error` as a failure callback - it's not properly bound.  If passes an
`Error` object, it will print the message and stack.