Detect and report docker load errors (#107)

We may want to have a more sophisticated way of dealing with this in the future
but this gives users a fighting chance of understand what went wrong + better
error reports for us.

Author: rainersigwald

Microsoft.NET.Build.Containers/CreateNewImage.cs

@@ -113,7 +113,15 @@ public override bool Execute()
 
         if (OutputRegistry.StartsWith("docker://"))
         {
-            LocalDocker.Load(image, ImageName, ImageTag, BaseImageName).Wait();
+            try
+            {
+                LocalDocker.Load(image, ImageName, ImageTag, BaseImageName).Wait();
+            }
+            catch (AggregateException ex) when (ex.InnerException is DockerLoadException dle)
+            {
+                Log.LogErrorFromException(dle, showStackTrace: false);
+                return !Log.HasLoggedErrors;
+            }
         }
         else
         {

Microsoft.NET.Build.Containers/DockerLoadException.cs

@@ -0,0 +1,23 @@
+using System.Runtime.Serialization;
+
+namespace Microsoft.NET.Build.Containers
+{
+    public class DockerLoadException : Exception
+    {
+        public DockerLoadException()
+        {
+        }
+
+        public DockerLoadException(string? message) : base(message)
+        {
+        }
+
+        public DockerLoadException(string? message, Exception? innerException) : base(message, innerException)
+        {
+        }
+
+        protected DockerLoadException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}

Microsoft.NET.Build.Containers/LocalDocker.cs

@@ -14,6 +14,7 @@ public static async Task Load(Image x, string name, string tag, string baseName)
         ProcessStartInfo loadInfo = new("docker", $"load");
         loadInfo.RedirectStandardInput = true;
         loadInfo.RedirectStandardOutput = true;
+        loadInfo.RedirectStandardError = true;
 
         using Process? loadProcess = Process.Start(loadInfo);
 
@@ -29,6 +30,11 @@ public static async Task Load(Image x, string name, string tag, string baseName)
         loadProcess.StandardInput.Close();
 
         await loadProcess.WaitForExitAsync();
+
+        if (loadProcess.ExitCode != 0)
+        {
+            throw new DockerLoadException($"Failed to load image to local Docker daemon. stdout: {await loadProcess.StandardError.ReadToEndAsync()}");
+        }
     }
 
     public static async Task WriteImageToStream(Image x, string name, string tag, Stream imageStream)