Make warnings elevated to errors distinguishable from actual errors

I think warnings elevated to errors should have different output compared to errors that are always errors. The NuGet team has received numerous complaints from people asking why something they don’t consider serious has failed their build, and we have to keep repeating that NuGet treats it as a warning and help them understand how their project has opted into warnings as errors.

I think if the error said “Warning As Error: NU1234” instead of just “Error: NU1234”, or “Error (elevated warning): NU1234”, “Error: NU1234 (elevated warning)” or something similar, customers would more quickly understand that their project configuration has asked for this. However, I suspect changing the message could cause problems with people who run regex on the build output, maybe the VS error list will be affected. So, I’d like input from other teams what might be a good approach, plus see if there’s any buy-in from other teams to do this in a consistent way