Allow type | None syntax on python 3.9

Author: ianthomas23

ipykernel/shellchannel.py

@@ -1,4 +1,5 @@
 """A thread for a shell channel."""
+from __future__ import annotations
 
 from typing import Any
 

ipykernel/utils.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from typing import Any
 
 import zmq

tests/test_connect.py

@@ -2,7 +2,6 @@
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
-
 import errno
 import json
 import os

tests/test_subshells.py

@@ -2,6 +2,8 @@
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
+from __future__ import annotations
+
 import platform
 import time