Fix error handling After the fix to #2500, we could get "Failing due to -Werror." but no warnings printed. Now we don't fail in that case.
Fix error handling
After the fix to #2500, we could get "Failing due to -Werror." but no
warnings printed. Now we don't fail in that case.

lukexi/ghc-7.8-arm64,elieux/ghc,gcampax/ghc,ghc-android/ghc,olsner/ghc,oldmanmike/ghc,christiaanb/ghc,AlexanderPankiv/ghc,olsner/ghc,vikraman/ghc,nushio3/ghc,shlevy/ghc,fmthoma/ghc,sgillespie/ghc,nomeata/ghc,jstolarek/ghc,TomMD/ghc,gcampax/ghc,mfine/ghc,da-x/ghc,hferreiro/replay,holzensp/ghc,mcmaniac/ghc,oldmanmike/ghc,spacekitteh/smcghc,mcmaniac/ghc,GaloisInc/halvm-ghc,gridaphobe/ghc,christiaanb/ghc,vTurbine/ghc,nomeata/ghc,vikraman/ghc,mfine/ghc,snoyberg/ghc,acowley/ghc,ghc-android/ghc,olsner/ghc,nushio3/ghc,anton-dessiatov/ghc,tjakway/ghcjvm,shlevy/ghc,forked-upstream-packages-for-ghcjs/ghc,vikraman/ghc,ezyang/ghc,acowley/ghc,TomMD/ghc,gridaphobe/ghc,anton-dessiatov/ghc,sgillespie/ghc,forked-upstream-packages-for-ghcjs/ghc,ekmett/ghc,fmthoma/ghc,jstolarek/ghc,forked-upstream-packages-for-ghcjs/ghc,fmthoma/ghc,sgillespie/ghc,snoyberg/ghc,ghc-android/ghc,nathyong/microghc-ghc,bitemyapp/ghc,nomeata/ghc,ekmett/ghc,siddhanathan/ghc,acowley/ghc,TomMD/ghc,christiaanb/ghc,frantisekfarka/ghc-dsi,mettekou/ghc,wxwxwwxxx/ghc,christiaanb/ghc,forked-upstream-packages-for-ghcjs/ghc,sgillespie/ghc,tjakway/ghcjvm,christiaanb/ghc,sgillespie/ghc,shlevy/ghc,mfine/ghc,frantisekfarka/ghc-dsi,TomMD/ghc,elieux/ghc,lukexi/ghc,wxwxwwxxx/ghc,tjakway/ghcjvm,vikraman/ghc,nathyong/microghc-ghc,ezyang/ghc,vTurbine/ghc,nkaretnikov/ghc,siddhanathan/ghc,nkaretnikov/ghc,anton-dessiatov/ghc,olsner/ghc,oldmanmike/ghc,siddhanathan/ghc,nomeata/ghc,GaloisInc/halvm-ghc,ekmett/ghc,da-x/ghc,tjakway/ghcjvm,shlevy/ghc,TomMD/ghc,oldmanmike/ghc,jstolarek/ghc,ryantm/ghc,TomMD/ghc,ezyang/ghc,fmthoma/ghc,ryantm/ghc,ilyasergey/GHC-XAppFix,GaloisInc/halvm-ghc,vikraman/ghc,frantisekfarka/ghc-dsi,TomMD/ghc,nathyong/microghc-ghc,urbanslug/ghc,green-haskell/ghc,ml9951/ghc,ryantm/ghc,AlexanderPankiv/ghc,lukexi/ghc,GaloisInc/halvm-ghc,green-haskell/ghc,lukexi/ghc,ezyang/ghc,mfine/ghc,mfine/ghc,GaloisInc/halvm-ghc,urbanslug/ghc,gridaphobe/ghc,GaloisInc/halvm-ghc,wxwxwwxxx/ghc,nathyong/microghc-ghc,AlexanderPankiv/ghc,lukexi/ghc-7.8-arm64,mcschroeder/ghc,anton-dessiatov/ghc,spacekitteh/smcghc,hferreiro/replay,snoyberg/ghc,lukexi/ghc-7.8-arm64,frantisekfarka/ghc-dsi,da-x/ghc,hferreiro/replay,acowley/ghc,ml9951/ghc,tibbe/ghc,ilyasergey/GHC-XAppFix,snoyberg/ghc,mcschroeder/ghc,lukexi/ghc-7.8-arm64,ezyang/ghc,gridaphobe/ghc,tibbe/ghc,sdiehl/ghc,gcampax/ghc,jstolarek/ghc,nathyong/microghc-ghc,anton-dessiatov/ghc,sdiehl/ghc,lukexi/ghc-7.8-arm64,nkaretnikov/ghc,nomeata/ghc,snoyberg/ghc,christiaanb/ghc,vTurbine/ghc,sdiehl/ghc,ml9951/ghc,urbanslug/ghc,vikraman/ghc,acowley/ghc,mettekou/ghc,green-haskell/ghc,acowley/ghc,holzensp/ghc,nushio3/ghc,mcschroeder/ghc,shlevy/ghc,anton-dessiatov/ghc,siddhanathan/ghc,ilyasergey/GHC-XAppFix,mfine/ghc,holzensp/ghc,vTurbine/ghc,da-x/ghc,AlexanderPankiv/ghc,snoyberg/ghc,bitemyapp/ghc,ml9951/ghc,wxwxwwxxx/ghc,ghc-android/ghc,fmthoma/ghc,nkaretnikov/ghc,elieux/ghc,wxwxwwxxx/ghc,ryantm/ghc,urbanslug/ghc,elieux/ghc,mettekou/ghc,nkaretnikov/ghc,ml9951/ghc,lukexi/ghc,acowley/ghc,olsner/ghc,ghc-android/ghc,sdiehl/ghc,sdiehl/ghc,nushio3/ghc,bitemyapp/ghc,holzensp/ghc,shlevy/ghc,ml9951/ghc,forked-upstream-packages-for-ghcjs/ghc,mettekou/ghc,elieux/ghc,gridaphobe/ghc,gcampax/ghc,spacekitteh/smcghc,jstolarek/ghc,nkaretnikov/ghc,ekmett/ghc,ezyang/ghc,anton-dessiatov/ghc,gridaphobe/ghc,ml9951/ghc,ghc-android/ghc,ekmett/ghc,da-x/ghc,snoyberg/ghc,gridaphobe/ghc,urbanslug/ghc,sdiehl/ghc,ghc-android/ghc,urbanslug/ghc,mcschroeder/ghc,elieux/ghc,ezyang/ghc,mcmaniac/ghc,siddhanathan/ghc,hferreiro/replay,hferreiro/replay,nathyong/microghc-ghc,mcschroeder/ghc,olsner/ghc,forked-upstream-packages-for-ghcjs/ghc,AlexanderPankiv/ghc,mfine/ghc,nathyong/microghc-ghc,ml9951/ghc,mettekou/ghc,sgillespie/ghc,oldmanmike/ghc,oldmanmike/ghc,sdiehl/ghc,mettekou/ghc,spacekitteh/smcghc,mcschroeder/ghc,frantisekfarka/ghc-dsi,gcampax/ghc,olsner/ghc,siddhanathan/ghc,vTurbine/ghc,shlevy/ghc,lukexi/ghc,forked-upstream-packages-for-ghcjs/ghc,ryantm/ghc,mcmaniac/ghc,sgillespie/ghc,tjakway/ghcjvm,gcampax/ghc,vTurbine/ghc,AlexanderPankiv/ghc,nushio3/ghc,hferreiro/replay,da-x/ghc,green-haskell/ghc,hferreiro/replay,fmthoma/ghc,fmthoma/ghc,tibbe/ghc,wxwxwwxxx/ghc,green-haskell/ghc,GaloisInc/halvm-ghc,AlexanderPankiv/ghc,vTurbine/ghc,christiaanb/ghc,da-x/ghc,wxwxwwxxx/ghc,nkaretnikov/ghc,tjakway/ghcjvm,bitemyapp/ghc,tibbe/ghc,siddhanathan/ghc,oldmanmike/ghc,holzensp/ghc,bitemyapp/ghc,nushio3/ghc,tjakway/ghcjvm,mcschroeder/ghc,elieux/ghc,ilyasergey/GHC-XAppFix,spacekitteh/smcghc,gcampax/ghc,nushio3/ghc,mettekou/ghc,mcmaniac/ghc,urbanslug/ghc,vikraman/ghc,tibbe/ghc