Trying to prepare your WatchKit project for the upcoming release? Well, Xcode (or more precisely xcodebuild) might have other plans:
CodeSign error: code signing is required for product type 'WatchKit App' in SDK 'iOS 8.2'
Luckily there is an "easy" way to fix this. Open your Xcode project with Xcode 6.1.1 (yes, you're reading right, the Xcode version that does not know about WatchKit apps, Download here), open the WatchKit App target, go to Build Settings and search for Code Signing Identity. It will probably say Don't Code Sign, and you want to change this to your correct certificates.
Save your project, commit your changes, and open the project again in Xcode 6.2. You won't see any changes - however, xcodebuild will now be able to successfully build and sign your app.
Awesome, isn't it?