gh-90971: suppress deprecation warning in `test_lib2to3`(GH-31464)

Fixes GH-90971

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Éric <merwok@netwok.org>

Lib/lib2to3/tests/__init__.py

@@ -1,8 +1,11 @@
 # Author: Collin Winter
 
 import os
+import warnings
 
 from test.support import load_package_tests
 
 def load_tests(*args):
-    return load_package_tests(os.path.dirname(__file__), *args)
+    with warnings.catch_warnings():
+        warnings.filterwarnings('ignore', category=DeprecationWarning, message='lib2to3')
+        return load_package_tests(os.path.dirname(__file__), *args)

Lib/lib2to3/tests/test_parser.py

@@ -92,10 +92,8 @@ class TestPgen2Caching(support.TestCase):
 from lib2to3.pgen2 import driver as pgen2_driver
 pgen2_driver.load_grammar(%r, save=True, force=True)
             """ % (grammar_sub_copy,)
-            msg = ("lib2to3 package is deprecated and may not be able "
-                   "to parse Python 3.10+")
             cmd = [sys.executable,
-                   f'-Wignore:{msg}:PendingDeprecationWarning',
+                   '-Wignore:lib2to3:DeprecationWarning',
                    '-c', code]
             subprocess.check_call( cmd, env=sub_env)
             self.assertTrue(os.path.exists(pickle_sub_name))