What is causing this on iOS 10 Build. ... Class PLBuildVersion is implemented in both

I'm getting this message when trying to update an iOS App to iOS 10, on XCode 8.

I have no idea how to solve the problem, even though the error message seems clear - there is no clue as to what I can do to fix it?

Class PLBuildVersion is implemented in both /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/D eveloper/SDKs/iPhoneSimulator.sdk/System/Library/PrivateFrameworks/AssetsLibrary Services.framework/AssetsLibraryServices (0x110c26910) and /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/D eveloper/SDKs/iPhoneSimulator.sdk/System/Library/PrivateFrameworks/PhotoLibraryS ervices.framework/PhotoLibraryServices (0x110a50210). One of the two will be used. Which one is undefined.