Adjust import timings test for python 3.12 (#8260)

Author: bdraco

tests/test_imports.py

@@ -28,6 +28,11 @@ def test_web___all__(pytester: pytest.Pytester) -> None:
     result.assert_outcomes(passed=0, errors=0)
 
 
+_TARGET_TIMINGS_BY_PYTHON_VERSION = {
+    "3.12": 250,  # 3.12 is expected to be a bit slower due to performance trade-offs
+}
+
+
 @pytest.mark.skipif(
     not sys.platform.startswith("linux") or platform.python_implementation() == "PyPy",
     reason="Timing is more reliable on Linux",
@@ -59,4 +64,7 @@ def test_import_time(pytester: pytest.Pytester) -> None:
         else:
             os.environ["PYTHONPATH"] = old_path
 
-    assert best_time_ms < 200
+    expected_time = _TARGET_TIMINGS_BY_PYTHON_VERSION.get(
+        f"{sys.version_info.major}.{sys.version_info.minor}", 200
+    )
+    assert best_time_ms < expected_time