Test improvements (#17428)

Retry adding package and print reason for failure

src/Tools/Microsoft.dotnet-openapi/src/Commands/BaseCommand.cs

@@ -200,12 +200,18 @@ namespace Microsoft.DotNet.OpenApi.Commands
                 var packageId = kvp.Key;
                 var version = urlPackages != null && urlPackages.ContainsKey(packageId) ? urlPackages[packageId] : kvp.Value;
 
+                await TryAddPackage(packageId, version, projectFile);
+            }
+        }
+
+        private async Task TryAddPackage(string packageId, string packageVersion, FileInfo projectFile)
+        {
             var args = new[] {
                 "add",
                 "package",
                 packageId,
                 "--version",
-                    version,
+                packageVersion,
                 "--no-restore"
             };
 
@@ -224,7 +230,7 @@ namespace Microsoft.DotNet.OpenApi.Commands
                 RedirectStandardOutput = true,
             };
 
-                var process = Process.Start(startInfo);
+            using var process = Process.Start(startInfo);
 
             var timeout = 20;
             if (!process.WaitForExit(timeout * 1000))
@@ -234,10 +240,12 @@ namespace Microsoft.DotNet.OpenApi.Commands
 
             if (process.ExitCode != 0)
             {
-                    Out.Write(process.StandardOutput.ReadToEnd());
+                var output = await process.StandardOutput.ReadToEndAsync();
-                    Error.Write(process.StandardError.ReadToEnd());
+                var error = await process.StandardError.ReadToEndAsync();
-                    throw new ArgumentException($"Could not add package `{packageId}` to `{projectFile.Directory}`");
+                await Out.WriteAsync(output);
-                }
+                await Error.WriteAsync(error);
+
+                throw new ArgumentException($"Could not add package `{packageId}` to `{projectFile.Directory}` due to: `{error}`");
             }
         }