test_urllibnet: make it so that transient_internet() applies to the

whole HTTP exchange, not only the opening.

Lib/test/test_urllibnet.py

@@ -43,7 +43,9 @@ class urlopenNetworkTests(unittest.TestCase):
 
     def urlopen(self, *args, **kwargs):
         resource = args[0]
-        with support.transient_internet(resource):
+        cm = support.transient_internet(resource)
+        cm.__enter__()
+        self.addCleanup(cm.__exit__, None, None, None)
         return urllib.request.urlopen(*args, **kwargs)
 
     def test_basic(self):
@@ -135,7 +137,9 @@ class urlretrieveNetworkTests(unittest.TestCase):
 
     def urlretrieve(self, *args):
         resource = args[0]
-        with support.transient_internet(resource):
+        cm = support.transient_internet(resource)
+        cm.__enter__()
+        self.addCleanup(cm.__exit__, None, None, None)
         return urllib.request.urlretrieve(*args)
 
     def test_basic(self):