add comment for pylint disable

Author: jakkdl

tests/test_connection.py

@@ -443,6 +443,7 @@ async def test_handshake_exception_before_accept() -> None:
     async def handler(request):
         raise ValueError()
 
+    # pylint fails to resolve that BaseExceptionGroup will always be available
     with pytest.raises((BaseExceptionGroup, ValueError)) as exc:  # pylint: disable=possibly-used-before-assignment
         async with trio.open_nursery() as nursery:
             server = await nursery.start(serve_websocket, handler, HOST, 0,