pre-commit: add isort hook and apply (#354)

tests/util.py

@@ -1,11 +1,20 @@
 import asyncio
-from dataclasses import dataclass
 import importlib
 import os
-from pathlib import Path
 import sys
+from dataclasses import dataclass
+from pathlib import Path
 from types import ModuleType
-from typing import Callable, Dict, Generator, List, Optional, Tuple, Union
+from typing import (
+    Callable,
+    Dict,
+    Generator,
+    List,
+    Optional,
+    Tuple,
+    Union,
+)
+
 
 os.environ["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = "python"