NullReferenceException from PublishArtifactsInManifest in ASP.NET Core build

• This issue is blocking
• This issue is causing unreasonable pain

The ASP.NET Core build at https://dev.azure.com/dnceng/internal/_build/results?buildId=1373561&view=logs&j=226748d0-f812-5437-d3f0-2dd291f5666e&t=bad11196-972e-5d03-45a8-9db526506073&l=51 failed with the following error:

2021-09-20T23:33:54.2609031Z D:\a\1\s\.packages\microsoft.dotnet.arcade.sdk\7.0.0-beta.21466.4\tools\SdkTasks\PublishArtifactsInManifest.proj(123,5): error : Object reference not set to an instance of an object.
2021-09-20T23:33:54.2709639Z ##[error].packages\microsoft.dotnet.arcade.sdk\7.0.0-beta.21466.4\tools\SdkTasks\PublishArtifactsInManifest.proj(123,5): error : Object reference not set to an instance of an object.
2021-09-20T23:33:54.2722187Z D:\a\1\s\.packages\microsoft.dotnet.arcade.sdk\7.0.0-beta.21466.4\tools\SdkTasks\PublishArtifactsInManifest.proj(123,5): error : Publishing symbols failed : 
2021-09-20T23:33:54.2727023Z ##[error].packages\microsoft.dotnet.arcade.sdk\7.0.0-beta.21466.4\tools\SdkTasks\PublishArtifactsInManifest.proj(123,5): error : Publishing symbols failed : 

This only happened once, so it seems to be an intermittent issue. There are binlogs at https://dev.azure.com/dnceng/internal/_build/results?buildId=1373689&view=artifacts&pathAsName=false&type=publishedArtifacts, in which I see the following:

So, it looks like the underlying issue is that the endpoint to which we’re trying to publish didn’t respond, or there was some other network issue.

Ideally, PublishArtifactsInManifest would report the underlying issue instead of throwing the NullReferenceException, so that we don’t risk blaming PublishArtifactsInManifest for this and can more directly get to the cause without going through binlogs.

[riarenas]

I believe https://github.com/dotnet/arcade/pull/7964 is already out to fix this.

[mikem8361]

We already have some fixes in PR (and approved) https://github.com/dotnet/arcade/pull/7964