Always run plugin within the poetry venv

meta_package_manager/tests/test_bar_plugin.py

@@ -170,7 +170,9 @@ class TestBarPlugin:
     def plugin_output_checks(self, checklist, extra_env=None):
         """Run the plugin script and check its output against the checklist."""
         process = subprocess.run(
-            bar_plugin.__file__,
+            # Force the plugin to be called within Poetry venv to not have it seeking
+            # for macOS's default Python.
+            ("poetry", "run", "python", bar_plugin.__file__),
             capture_output=True,
             encoding="utf-8",
             env=env_copy(extra_env),