When I tried to create a archive in Xcode 7.3 and to upload IPA for TestFlight. I got this error. I tried it multiple times and got the same error. I googled for it and got simple solution and it worked!!. And the solution is trying it after some time. Yes doing it after some time worked for me.
This may be due to network issue or Apple server issue or some thing else. But It works if you try after some time.