treat MSB3274 and MSB3275 as errors when building inside SharpDevelop

src/Main/SharpDevelop/Project/Build/BuildEngine.cs

@@ -158,6 +158,7 @@ namespace ICSharpCode.SharpDevelop.Project
 			
 			public void ReportError(BuildError error)
 			{
+				TransformBuildError(error);
 				if (error.IsWarning) {
 					if (perNodeProgressMonitor.Status != OperationStatus.Error)
 						perNodeProgressMonitor.Status = OperationStatus.Warning;
@@ -166,6 +167,27 @@ namespace ICSharpCode.SharpDevelop.Project
 				}
 				engine.ReportError(this, error);
 			}
+
+			void TransformBuildError(BuildError error)
+			{
+				if (error.IsWarning) {
+					// treat "MSB3274: The primary reference "{0}" could not be resolved because it was 
+					// built against the "{1}" framework. This is a higher version than the currently 
+					// targeted framework "{2}"." as error.
+					if ("MSB3274".Equals(error.ErrorCode, StringComparison.OrdinalIgnoreCase)) {
+						error.IsWarning = false;
+						return;
+					}
+					// treat "MSB3275: The primary reference "{0}" could not be resolved because it has
+					// an indirect dependency on the assembly "{1}" which was built against the "{2}"
+					// framework. This is a higher version than the currently targeted framework "{3}"."
+					// as error.
+					if ("MSB3275".Equals(error.ErrorCode, StringComparison.OrdinalIgnoreCase)) {
+						error.IsWarning = false;
+						return;
+					}
+				}
+			}
 			
 			public void ReportMessage(RichText message)
 			{