bpo-40275: Use new test.support helper submodules in tests (GH-21219)

diff --git a/Lib/test/test_smtpd.py b/Lib/test/test_smtpd.py
index 3be7739..d5d5abf 100644
--- a/Lib/test/test_smtpd.py
+++ b/Lib/test/test_smtpd.py
@@ -2,6 +2,7 @@
 import textwrap
 from test import support, mock_socket
 from test.support import socket_helper
+from test.support import warnings_helper
 import socket
 import io
 import smtpd
@@ -714,49 +715,49 @@
                          b'recognized\r\n')
 
     def test_attribute_deprecations(self):
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__server
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__server = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__line
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__line = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__state
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__state = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__greeting
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__greeting = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__mailfrom
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__mailfrom = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__rcpttos
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__rcpttos = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__data
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__data = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__fqdn
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__fqdn = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__peer
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__peer = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__conn
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__conn = 'spam'
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             spam = self.channel._SMTPChannel__addr
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             self.channel._SMTPChannel__addr = 'spam'
 
 @unittest.skipUnless(socket_helper.IPV6_ENABLED, "IPv6 not enabled")