A few days ago Xcode 8.3 was released with Swift 3.1. You'll probably need to update some or all of the modules you've built so far as running swift build on any project with a Swift 3.0.x compiled library won't work. Notably, if you haven't been following the SwiftPM evolution, the folder where packages are stored has changed too. Instead of saving them at the root of your project's in the Packages directory, now the SwiftPM will keep a copy of all your dependencies in the .build folder. The Packages directory will still be used for packages you want to edit yourself, though.

Changing topic, whether or not you'll be able to buy a ticket for the conference, if you're in San Jose or nearby during the WWDC week, make sure to check out this page Apple has put up with the other events happening in parallel!

Gianluca Tranchedone