gh-128550: TaskGroup: cancel tasks added to set after aborting

Author: graingert

Lib/asyncio/taskgroups.py

@@ -205,6 +205,8 @@ def create_task(self, coro, *, name=None, context=None):
         else:
             self._tasks.add(task)
             task.add_done_callback(self._on_task_done)
+            if self._aborting:
+                task.cancel()
         return task
 
     # Since Python 3.8 Tasks propagate all exceptions correctly,