In Xcode 6.3, I got this error when trying to run an iOS project written in Swift on a real device.
App installation failed
c
This looks like another time waster courtesy of Apple's amazingly high class development team. On iOS11 Xcode9 (pick your beta, any one works) this will happen randomly. Appears to be more frequent if you dare to switch apps while compiling. Just build again and stare at xcode - it'll work the second time without fail in my experience.