For me this solutiuon is to disable Bitcode in the Build settings for the iOS Target.
Background
The issue started after updating to Xcode 7.3 and OS X 10.11.4.
On Monday 21st I succesfully submitted a build with Xcode 7.2.1 and OS X 10.11.3.
Tuesday 22nd submitting failed.
I awaited the Apple Support suggested 24 hours, and uploaded a new build today. No luck.
After these 2 erroneous builds, I disabled Bitcode and submitted a new build. After 30 minutes it completed processing succesfully.
To somehow determine whether this solved it, I submitted a new build with Bitcode disabled. This failed with "There was an error importing this build".
I have sent a detailed report to Apple Support.