Transport sockets do not support shutdown() method

• uvloop version: 0.12.2
• Python version: 3.5.3
• Platform: Debian 9
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: yes

An attempt to use shutdown method of transport socket causes following exception:

source_traceback: Object created at (most recent call last):
  File "/usr/local/bin/ssh-tarpit", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.5/dist-packages/ssh_tarpit/__main__.py", line 109, in main
    loop.run_until_complete(amain(args, loop))
  File "/usr/lib/python3.5/asyncio/streams.py", line 238, in connection_made
    self._stream_writer)
  File "/usr/local/lib/python3.5/dist-packages/ssh_tarpit/server.py", line 52, in _spawn
    self._loop.create_task(self.handler(reader, writer)))
Traceback (most recent call last):
  File "/usr/lib/python3.5/asyncio/tasks.py", line 239, in _step
    result = coro.send(None)
  File "/usr/lib/python3.5/asyncio/coroutines.py", line 125, in send
    return self.gen.send(value)
  File "/usr/local/lib/python3.5/dist-packages/ssh_tarpit/server.py", line 38, in handler
    sock.shutdown(socket.SHUT_RD)
  File "uvloop/pseudosock.pyx", line 155, in uvloop.loop.PseudoSocket.shutdown
  File "uvloop/pseudosock.pyx", line 19, in uvloop.loop.PseudoSocket._na
TypeError: transport sockets do not support shutdown() method

Such behavior is not observed with default event loop.

Read uvloop/pseudosock.pyx at PseudoSocket.shutdown and the _na path shown in the traceback; begin by reproducing the socket shutdown call under the reported Python and uvloop versions. Done means the transport socket handles shutdown without the reported TypeError and matches the default event loop's behavior.