GH-93850: Fix test_asyncio exception ignored tracebacks (GH-93854)

(cherry picked from commit b415c5f)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

Author: miss-islington

Lib/test/test_asyncio/test_runners.py

@@ -45,6 +45,9 @@ class BaseTest(unittest.TestCase):
     def new_loop(self):
         loop = asyncio.BaseEventLoop()
         loop._process_events = mock.Mock()
+        # Mock waking event loop from select
+        loop._write_to_self = mock.Mock()
+        loop._write_to_self.return_value = None
         loop._selector = mock.Mock()
         loop._selector.select.return_value = ()
         loop.shutdown_ag_run = False