UIControlState.Normal is Unavailable

Previously for UIButton instances, you were able to pass in UIControlState.Normal for setTitle or setImage. .Normal is no longer available, what should I use instead?

let btn = UIButton(frame: CGRect(x: 0, y: 0, width: 20, height: 20))
btn.setTitle("title", for: .Normal) // does not compile

^{(This is a canonical Q&A pair to prevent the flood of duplicate questions related to this UIButton and UIControl changes with iOS 10 and Swift 3)}