chore: use from __future__ import annotations

unit_test/main_tests/conftest.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import contextlib
 import platform as platform_module
 import subprocess

unit_test/main_tests/main_options_test.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 from fnmatch import fnmatch
 from pathlib import Path

unit_test/main_tests/main_platform_test.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 import pytest

unit_test/main_tests/main_requires_python_test.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 import textwrap