title: Exception ignored in message on program exit
body: <p>I initially wanted to do async stream communication on windows. </p>
  
  <pre><code>from asyncio import *
  from asyncio.subprocess import PIPE, STDOUT, DEVNULL
  import sys
  
  async def test(exe):
    inst = await create_subprocess_exec(exe, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
    inst.stdin.close()
    inst.wait()
  
  # for subprocess' pipes on Windows
  def initialize_async():
    if sys.platform == 'win32':
      set_event_loop(ProactorEventLoop())
    return get_event_loop()
  
  loop = initialize_async()
  loop.run_until_complete(test('attrib.exe'))
  loop.close()
  </code></pre>
  
  <p>The above code generates the following.</p>
  
  <pre><code>Exception ignored in: &lt;bound method BaseSubprocessTransport.__del__ of &lt;_WindowsSubprocessTransport closed pid=65088 running stdin=&lt;_ProactorWritePipeTransport closed&gt; stdout=&lt;_ProactorReadPipeTransport closing fd=476 read=&lt;_OverlappedFuture cancelled&gt;&gt;&gt;&gt;
  Traceback (most recent call last):
    File "C:\Program Files\Python36\lib\asyncio\base_subprocess.py", line 132, in __del__
      self.close()
    File "C:\Program Files\Python36\lib\asyncio\base_subprocess.py", line 106, in close
      proto.pipe.close()
    File "C:\Program Files\Python36\lib\asyncio\proactor_events.py", line 84, in close
      self._loop.call_soon(self._call_connection_lost, None)
    File "C:\Program Files\Python36\lib\asyncio\base_events.py", line 573, in call_soon
      self._check_closed()
    File "C:\Program Files\Python36\lib\asyncio\base_events.py", line 357, in _check_closed
      raise RuntimeError('Event loop is closed')
  RuntimeError: Event loop is closed
  Exception ignored in: &lt;object repr() failed&gt;
  Traceback (most recent call last):
    File "C:\Program Files\Python36\lib\asyncio\proactor_events.py", line 95, in __del__
      warnings.warn("unclosed transport %r" % self, ResourceWarning,
    File "C:\Program Files\Python36\lib\asyncio\proactor_events.py", line 54, in __repr__
      info.append('fd=%s' % self._sock.fileno())
    File "C:\Program Files\Python36\lib\asyncio\windows_utils.py", line 152, in fileno
      raise ValueError("I/O operatioon on closed pipe")
  ValueError: I/O operatioon on closed pipe
  </code></pre>
  
  <p>How can I remove this error? stdin.close and wait seems not sufficient.</p>