code: function openUsbDevice(usbDevice, { dfuMode = false } = {}) {
  	if (!dfuMode && usbDevice.isInDfuMode) {
  		return when.reject(new Error('The device should not be in DFU mode'));
  	}
  	return when.resolve().then(() => usbDevice.open())
  		.catch(e => handleDeviceOpenError(e));
  }
docs: Open a USB device.
  
  This function checks whether the user has necessary permissions to access the device.
  Use this function instead of particle-usb's Device.open().
  
  @param {Object} usbDevice USB device.
  @param {Object} options Options.
  @param {Boolean} [options.dfuMode] Set to `true` if the device can be in DFU mode.
  @return {Promise}