Script Shutdown() doesn't stop running python script

Description

The Python script is running a loop in a thread. The runtime.Shutdown() should stop the running python script. It does not.

Steps to Reproduce

This example will demonstrate how the python script contains a loop in a thread. A button to stop the running script by calling Shutdown() is not doing anything.

     public class StreamWriteEvent : MemoryStream {

      public event EventHandler<string> OnNewText;

      public override void Write(byte[] buffer, int offset, int count) {

        OnNewText?.Invoke(this, Encoding.Default.GetString(buffer, offset, count));

        base.Write(buffer, offset, count);
      }

      public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) {

        OnNewText?.Invoke(this, Encoding.Default.GetString(buffer, offset, count));

        return base.WriteAsync(buffer, offset, count, cancellationToken);
      }

      public override void WriteByte(byte value) {

        OnNewText?.Invoke(this, value.ToString());

        base.WriteByte(value);
      }

      public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state) {

        OnNewText?.Invoke(this, Encoding.Default.GetString(buffer, offset, count));

        return base.BeginWrite(buffer, offset, count, callback, state);
      }
    }

    ScriptEngine _engine;
    ScriptScope _scope;

    // Run a python script in a new thread
    private void button2_Click(object sender, EventArgs e) {

      Thread ts = new Thread(runScript);
      ts.Start();
    }

    // This thread is running the python script
    void runScript() {

      var streamWriter = new StreamWriteEvent();
      streamWriter.OnNewText += StreamWriter_OnNewText;

      _engine = IronPython.Hosting.Python.CreateEngine();

      _engine.Runtime.IO.SetErrorOutput(streamWriter, Encoding.ASCII);
      _engine.Runtime.IO.SetOutput(streamWriter, Encoding.ASCII);

      _scope = _engine.CreateScope();

      // Run a script that loops
      // We will test both capturing the output stream & the Shutdown command to stop the running script
      var sc = _engine.CreateScriptSourceFromString(@"
while True:
  print('This should output something')
");

      var ret = sc.Execute(_scope);

      // This doesn't do anything. It doesn't stop the running script.
      Console.WriteLine("Shut down");
    }

    private void StreamWriter_OnNewText(object sender, string e) {

      // This should output but never does
      Console.WriteLine("From steam writer" + e);
    }

    // This is the button that should stop the running python script
    private void button3_Click(object sender, EventArgs e) {

      Console.WriteLine("Shutting down...");

      // This shutdown command doesn't work. The script will continue running.
      _scope.Engine.Runtime.Shutdown();
    }

Expected behavior:
The running python script should stop

Actual behavior:
The running python script does not stop

Versions

3.4.0-alpha1 for .Net Framework 4.7.2 from nuget

Start by reproducing the example with ScriptEngine, ScriptScope, CreateScriptSourceFromString, and Runtime.Shutdown, focusing on the loop running in a separate thread. Trace the shutdown entry point and verify that the running Python script stops and the execution reaches the “Shut down” message.