bpo-34587, test_socket: remove RDSTest.testCongestion() (GH-9277)

The test tries to fill the receiver's socket buffer and expects an
error. But the RDS protocol doesn't require that. Moreover, the Linux
implementation of RDS expects that the producer of the messages
reduces its rate, it's not the role of the receiver to trigger an
error.

The test fails on Fedora 28 by design, so remove it.
(cherry picked from commit 7484bdf)

Co-authored-by: Victor Stinner <[email protected]>

Author: miss-islington

Lib/test/test_socket.py

@@ -1773,33 +1773,6 @@ def _testSelect(self):
         self.data = b'select'
         self.cli.sendto(self.data, 0, (HOST, self.port))
 
-    def testCongestion(self):
-        # wait until the sender is done
-        self.evt.wait()
-
-    def _testCongestion(self):
-        # test the behavior in case of congestion
-        self.data = b'fill'
-        self.cli.setblocking(False)
-        try:
-            # try to lower the receiver's socket buffer size
-            self.cli.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 16384)
-        except OSError:
-            pass
-        with self.assertRaises(OSError) as cm:
-            try:
-                # fill the receiver's socket buffer
-                while True:
-                    self.cli.sendto(self.data, 0, (HOST, self.port))
-            finally:
-                # signal the receiver we're done
-                self.evt.set()
-        # sendto() should have failed with ENOBUFS
-        self.assertEqual(cm.exception.errno, errno.ENOBUFS)
-        # and we should have received a congestion notification through poll
-        r, w, x = select.select([self.serv], [], [], 3.0)
-        self.assertIn(self.serv, r)
-
 
 @unittest.skipUnless(thread, 'Threading required for this test.')
 class BasicTCPTest(SocketConnectedTest):

Misc/NEWS.d/next/Tests/2018-09-13-20-58-07.bpo-34587.rCcxp3.rst

@@ -0,0 +1,5 @@
+test_socket: Remove RDSTest.testCongestion(). The test tries to fill the
+receiver's socket buffer and expects an error. But the RDS protocol doesn't
+require that. Moreover, the Linux implementation of RDS expects that the
+producer of the messages reduces its rate, it's not the role of the receiver to
+trigger an error. The test fails on Fedora 28 by design, so just remove it.