Can't get close_info from synchronous connection

[vitaly-krugl]

If connection fails during construction of synchronous RabbitConnection or Connection, there is no way to get the close_info.

def onConnectionClosed(): # no arg passed to callback, so no way to get close_info
  pass

# Here, if connection set-up/negotiation/etc. fails in the constructor, `conn` is not set up, 
# so we can't get close_info directly from the instance
conn = RabbitConnection(user="unknownuser", close_cb=onConnectionClosed)