bpo-40275: Move transient_internet from test.support to socket_helper (GH-19711)

diff --git a/Lib/test/test_urllibnet.py b/Lib/test/test_urllibnet.py
index 422d529..28680aa 100644
--- a/Lib/test/test_urllibnet.py
+++ b/Lib/test/test_urllibnet.py
@@ -1,5 +1,6 @@
 import unittest
 from test import support
+from test.support import socket_helper
 
 import contextlib
 import socket
@@ -27,7 +28,7 @@
         self.addCleanup(urllib.request.urlcleanup)
 
         domain = urllib.parse.urlparse(support.TEST_HTTP_URL).netloc
-        with support.transient_internet(domain):
+        with socket_helper.transient_internet(domain):
             f = urllib.request.urlopen(support.TEST_HTTP_URL)
             f.read()
 
@@ -56,7 +57,7 @@
     @contextlib.contextmanager
     def urlopen(self, *args, **kwargs):
         resource = args[0]
-        with support.transient_internet(resource):
+        with socket_helper.transient_internet(resource):
             r = urllib.request.urlopen(*args, **kwargs)
             try:
                 yield r
@@ -98,7 +99,7 @@
     def test_getcode(self):
         # test getcode() with the fancy opener to get 404 error codes
         URL = self.url + "XXXinvalidXXX"
-        with support.transient_internet(URL):
+        with socket_helper.transient_internet(URL):
             with self.assertWarns(DeprecationWarning):
                 open_url = urllib.request.FancyURLopener().open(URL)
             try:
@@ -156,7 +157,7 @@
     @contextlib.contextmanager
     def urlretrieve(self, *args, **kwargs):
         resource = args[0]
-        with support.transient_internet(resource):
+        with socket_helper.transient_internet(resource):
             file_location, info = urllib.request.urlretrieve(*args, **kwargs)
             try:
                 yield file_location, info