tests: expect free-threaded import warnings (#5680)

* tests: expect free-threaded import warnings

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update tests/test_cpp_conduit.py

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgkio@gmail.com>

* Update tests/test_cpp_conduit.py

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgkio@gmail.com>

tests/pytest.ini

@@ -20,4 +20,3 @@ filterwarnings =
     # bogus numpy ABI warning (see numpy/#432)
     ignore:.*numpy.dtype size changed.*:RuntimeWarning
     ignore:.*numpy.ufunc size changed.*:RuntimeWarning
-    default:The global interpreter lock:RuntimeWarning

tests/test_cpp_conduit.py

@@ -2,15 +2,32 @@
 
 from __future__ import annotations
 
-import exo_planet_c_api
-import exo_planet_pybind11
-import home_planet_very_lonely_traveler
+import importlib
+import sys
+
 import pytest
 
 import env
 from pybind11_tests import cpp_conduit as home_planet
 
 
+def import_warns_freethreaded(name):
+    if name not in sys.modules and not getattr(sys, "_is_gil_enabled", lambda: True)():
+        with pytest.warns(
+            RuntimeWarning, match=f"has been enabled to load module '{name}'"
+        ):
+            return importlib.import_module(name)
+
+    return importlib.import_module(name)
+
+
+exo_planet_c_api = import_warns_freethreaded("exo_planet_c_api")
+exo_planet_pybind11 = import_warns_freethreaded("exo_planet_pybind11")
+home_planet_very_lonely_traveler = import_warns_freethreaded(
+    "home_planet_very_lonely_traveler"
+)
+
+
 def test_traveler_getattr_actually_exists():
     t_h = home_planet.Traveler("home")
     assert t_h.any_name == "Traveler GetAttr: any_name luggage: home"