I'm trying to convert swift 2 to swift 4 but macOS mojave 10.14 isn't letting me open xcode 8. Any ideas on other ways to convert?the error is :Xcode 8 cannot be opened because of a problem.Check with developer to make sure Xcode 8 works with this version of macOS. You may need to reinstall the application. Be sure to install any available updates for the application and macOS.