Add fast-fail package creation assertion in wrong-mapped-feed test

Agent-Logs-Url: https://github.com/NuGet/NuGet.Client/sessions/69387abc-7df5-4ffa-ba29-f76c06e50ea5

Co-authored-by: nkolev92 <[email protected]>

Author: Copilot

test/NuGet.Tests.Apex/NuGet.Tests.Apex/NuGetEndToEndTests/NuGetConsoleTestCase.cs

@@ -503,6 +503,7 @@ public async Task InstallPackageForPC_PackageSourceMapping_WithWrongMappedFeed_F
             var packageVersion = "1.0.0";
 
             await CommonUtility.CreatePackageInSourceAsync(simpleTestPathContext.PackageSource, packageName, packageVersion);
+            Assert.IsTrue(File.Exists(Path.Combine(simpleTestPathContext.PackageSource, $"{packageName}.{packageVersion}.nupkg")));
 
             CommonUtility.CreateConfigurationFile(Path.Combine(solutionDirectory, "NuGet.config"), $@"<?xml version=""1.0"" encoding=""utf-8""?>
 <configuration>