AsyncErrors.swift

public enum Producer<A> {
    case Value(A)
    case Error(ErrorType)
    
    func produce() throws -> A {
        switch self {
        case let .Value(x):
            return x
        case let .Error(y):
            throw y
        }
    }
}

 //Signature in method
func getActionable(resultCallback: (Producer<Image> -> Void))

//Use
do {
    self.image = try res.produce()
    self.updateContent()
}
catch {
    print("Image unavailable")
    //Set error image
}