test that http.client _tunnel closes the response on exceptions

Lib/test/test_httplib.py

@@ -2383,12 +2383,33 @@ def test_tunnel_debuglog(self):
 
         self.conn.set_debuglevel(1)
         self.conn._create_connection = self._create_connection(response_text)
+        self.conn.set_tunnel("destination.com")
+        self.conn.request('HEAD', '/', '')
+
+
+    def test_tunnel_leak(self):
+        sock = None
+
+        def _create_connection(address, timeout=None, source_address=None):
+            nonlocal sock
+            sock = FakeSocket(
+                'HTTP/1.1 404 NOT FOUND\r\n\r\n',
+                host=address[0],
+                port=address[1],
+            )
+            return sock
+
+        self.conn._create_connection = _create_connection
         self.conn.set_tunnel('destination.com')
+        exc = None
+        try:
+            self.conn.request('HEAD', '/', '')
+        except OSError as e:
+            # keeping a reference to exc keeps response alive in the traceback
+            exc = e
+        self.assertIsNotNone(exc)
+        self.assertTrue(sock.file_closed)
 
-        with support.captured_stdout() as output:
-            self.conn.request('PUT', '/', '')
-        lines = output.getvalue().splitlines()
-        self.assertIn('header: {}'.format(expected_header), lines)
 
 
 if __name__ == '__main__':