pydev can't debug in ThreadingHTTPServer

[kanehekili]

Running latest pydev in Eclipse 4.17 with python 3.9.
Have a small ThreadingHTTPServer that runs its loop in "server_forever". All code invoked by the server (like do_GET) are not reachable by the debugger any more.
Here a snippet, that will prevent debugging any further code:

        MyHTTPHandler.AppConnector = SomePlugin()
        server = ThreadingHTTPServer(('', int(port)),MyHTTPHandler)
        print('started httpserver...')
        server.serve_forever()

         class MyHTTPHandler(SimpleHTTPRequestHandler):
         def do_GET(self):
              print("Do Get") #will not stop on breakpoint

Using a simple "HttpServer" will work. The test can be invoked with:
curl localhost:<port>/Some.Text

[kanehekili]

The eclipse resources have to be deleted, which leads to reimporting the workspace. It doesn't make sense, but it helps