gh-150046: Fix `test_add_python_opts` to ignore `PYTHON*` env vars (#150089)

Avoid the runtime environment from affecting the tests' behaviours,
which notably checks the warning filters which can be controlled by
various PYTHON environment variables.

diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index 207b144d01d92559c58b575e6ee87d88a0942d9a..6d30d267cd5ad29c3e13832412b5026ca8a00d8d 100644 (file)
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -2287,7 +2287,8 @@ class ArgsTestCase(BaseTestCase):
         proc = subprocess.run(cmd,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.STDOUT,
-                              text=True)
+                              text=True,
+                              env=support.make_clean_env())
         self.assertEqual(proc.returncode, 0, proc)
 
     def test_add_python_opts(self):