It is an essential part of software development to handle errors correctly and iOS development is no different. It is important to reduce the impact of the error to your user and inform your user clearly if an action is required.
Here is the extension that you will need to add to your project and the implementation of how you would present the UIAlertController within a UIViewController class.
https://gist.github.com/rtking1993/26a4d36a69563f38f5e726949b6edd67