Improve error message for unexpectedly repeated fields

2 jobs for master in 52 minutes and 55 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #705399
compile
compilation

00:15:54

 
  Test
failed #705400
spec2 test
testing

00:37:00

 
Name Stage Failure
failed
testing Test There is an unknown failure, please try again
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