Fail if NuGet does not successfully download
Fail if NuGet does not successfully download

If there is an error in downloading NuGet, we want to fail early so
that we do not try to NuGet the CLR tests when NuGet does not exit.
We want to notify the user clearly that NuGet failed to download.

swaroop-sridhar/llilc,JosephTremoulet/llilc,pgavlin/llilc,tempbottle/llilc,russellhadley/llilc-original,russellhadley/llilc-original,AndyAyersMS/llilc,AndyAyersMS/llilc,russellhadley/llilc-original,pgavlin/llilc,richardlford/llilc,erozenfeld/llilc,BruceForstall/llilc,russellhadley/llilc,kyulee1/llilcjit,libengu/llilc,mmitche/llilc,marksantos/llilc,BruceForstall/llilc,richardlford/llilc,kyulee1/llilcjit,manu-silicon/llilc,marksantos/llilc,dotnet/llilc,dotnet/llilc,richardlford/llilc,dkorolev/llilc,dotnet/llilc,AndyAyersMS/llilc,swaroop-sridhar/llilc,dkorolev/llilc,adiaaida/llilc,JosephTremoulet/llilc,russellhadley/llilc-original,tempbottle/llilc,manu-silicon/llilc,mmitche/llilc,mmitche/llilc,tempbottle/llilc,adiaaida/llilc,BruceForstall/llilc,dkorolev/llilc,erozenfeld/llilc,JosephTremoulet/llilc,erozenfeld/llilc,marksantos/llilc,libengu/llilc,swaroop-sridhar/llilc,russellhadley/llilc,manu-silicon/llilc,mmitche/llilc,russellhadley/llilc,kyulee1/llilcjit,pgavlin/llilc,libengu/llilc,erozenfeld/llilc,adiaaida/llilc,libengu/llilc