While testing current 3.6 top of trunk, I noticed spurious error messages being reported that were not causing the tests to fail.  Investigating further, I found the culprit to be this issue's 6e14fd2a14cef6ea0709ad234ab41198c2195591.  Curiously, the errors aren't showing up on buildbots although I can reproduce 100% on both platforms I've tried: Debian Linux and macOS 10.12.  For some reason that needs to be explored, using -W on regrtest causes the messages to be suppressed and the buildbots use -w by default.

$ ./python
Python 3.6.1+ (remotes/upstream/3.6:76eabd3a21, Jun 10 2017, 15:20:44)
[GCC 6.3.0 20170516] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

# without -w or -W
$ ./python -m test test_asyncio
Run tests sequentially
0:00:00 [1/1] test_asyncio
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb55423b4>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb5542504>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb639f8bc>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb6126f84>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb6392fbc>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb671dedc>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
1 test OK.

Total duration: 13 sec
Tests result: SUCCESS

# with -w
$ ./python -m test -w test_asyncio
Run tests sequentially
0:00:00 [1/1] test_asyncio
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb4b15b5c>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb581f264>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb53f068c>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb65faf14>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb5816c04>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0xb582dea4>
transport: None
Traceback (most recent call last):
  File "/py/3x/unix/source/Lib/asyncio/sslproto.py", line 660, in _process_write_backlog
    self._transport.write(chunk)
AttributeError: 'NoneType' object has no attribute 'write'
1 test OK.

Total duration: 13 sec
Tests result: SUCCESS

# with -W -> no messages
$ ./python -m test -W test_asyncio
Run tests sequentially
0:00:00 [1/1] test_asyncio
1 test OK.

Total duration: 13 sec
Tests result: SUCCESS