aiohttp stub prints tracebacks for caught exceptions

[oherrala]

For example:

$ python3 run.py wrong.host.badssl.com 443
Exception in callback None()
handle: <Handle cancelled>
Traceback (most recent call last):
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/events.py", line 126, in _run
    self._callback(*self._args)
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/selector_events.py", line 731, in _read_ready
    self._protocol.data_received(data)
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/sslproto.py", line 503, in data_received
    ssldata, appdata = self._sslpipe.feed_ssldata(data)
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/sslproto.py", line 201, in feed_ssldata
    self._sslobj.do_handshake()
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 688, in do_handshake
    match_hostname(self.getpeercert(), self.server_hostname)
  File "/usr/local/Cellar/python3/3.6.0/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 321, in match_hostname
    % (hostname, ', '.join(map(repr, dnsnames))))
ssl.CertificateError: hostname 'wrong.host.badssl.com' doesn't match either of '*.badssl.com', 'badssl.com'
REJECT

Related issues:

• should catch ssl.CertificateError and reraise ClientConnectionError aio-libs/aiohttp#1116
• Don't pass ssl certivicate error to loop.call_exception_handler() python/asyncio#404
• Add Python 3 aiohttp TLS client #252

Upstream fix (not verified):

• Fix for #404 python/asyncio#460

[jdbertron]

Why are these issues all marked resolved when they're not. This is still happening.