Issue #12133: fix a ResourceWarning in urllib.request

AbstractHTTPHandler.do_open() of urllib.request closes the HTTP connection if
its getresponse() method fails with a socket error. Patch written by Ezio
Melotti.
diff --git a/Lib/test/test_urllib2.py b/Lib/test/test_urllib2.py
index e9fb2fc..58ef836 100644
--- a/Lib/test/test_urllib2.py
+++ b/Lib/test/test_urllib2.py
@@ -317,6 +317,9 @@
     def getresponse(self):
         return MockHTTPResponse(MockFile(), {}, 200, "OK")
 
+    def close(self):
+        pass
+
 class MockHandler:
     # useful for testing handler machinery
     # see add_ordered_mock_handlers() docstring