Solution : Delete the existing app on the device and try again.
Note : You don't have to do this all the time. It happens only when a version of the app is installed from the AppStore or from an Ad-hoc source like Testflight.
I hadn't seen this error before, but it happened to me on XCode - version 6.3.1 (6D1002) with an iPad Air. But around the internet it seems to happen to iPhone 6 and 6 Plus too.