Fix type annotation for py38

Author: stefanv

spin/__main__.py

@@ -6,6 +6,7 @@
 import sys
 import textwrap
 import traceback
+from typing import Union
 
 import click
 
@@ -30,7 +31,7 @@
 )
 
 
-def _detect_config_dir(path: pathlib.Path) -> pathlib.Path | None:
+def _detect_config_dir(path: pathlib.Path) -> Union[pathlib.Path, None]:
     path = path.resolve()
     files = os.listdir(path)
     if any(f in files for f in config_filenames):