版权声明：本文为陈云峰(www.swifty.cc)原创文章，未经允许不得转载。 https://blog.csdn.net/feosun/article/details/82801430
Increase the version of Swift for the libraries: Chatto and ChattoAdditions.
The main project has swift 3.3 version. But I can use libraries with swift 4.
Steps to fix problem:
Choose Pods in Project navigator.
Choose target: ChattoAdditions (Chatto)
Change Swift Language Version to Swift 4.1
Rebuild project (Clean & Build)
