If you ever get this error while doing autolayout, catch it by setting a symbolic break point.

Screen Shot 2017-01-13 at 9.01.54 AM.png

Can also add an action like this

Screen Shot 2017-01-13 at 9.09.40 AM.png

And then see in output like this

Screen Shot 2017-01-13 at 9.10.43 AM.png

The way to fix it is to dispatch things on the mainthread and not in the background.

dispatch_async(dispatch_get_main_queue(), ^{
    // code here