bpo-44498: suppress DeprecationWarnings for asynchat, asyncore and smtpd in tests (GH-26905) (GH-26907)

(cherry picked from commit 22e7effad571f8e524d2f71ff55bbf2a25306753)

Co-authored-by: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 8b3d1fe..684e308 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2,8 +2,6 @@
 # does add tests for a few functions which have been determined to be more
 # portable than they had been thought to be.
 
-import asynchat
-import asyncore
 import codecs
 import contextlib
 import decimal
@@ -39,6 +37,11 @@
 from test.support import warnings_helper
 from platform import win32_is_iot
 
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asynchat
+    import asyncore
+
 try:
     import resource
 except ImportError: