Log Message:
py-autobahn: Update to 18.6.1.

Notably this version fixes the build with python37.

18.6.1
  fix: implement abort argument for asyncio in
  WebSocketAdapterProtocol._closeConnection (#1012)

18.5.2
  fix: security (DoS amplification): a WebSocket server with permessage-deflate
  turned on could be induced to waste extra memory through a \ 
"zip-bomb" style
  attack. Setting a max-message-size will now stop deflating compressed data when
  the max is reached (instead of consuming all compressed data first). This could
  be used by a malicious client to make the server waste much more memory than
  the bandwidth the client uses.

18.5.1
  fix: asyncio/rawsocket buffer processing
  fix: example failures due to pypy longer startup time (#996)
  fix: add on_welcome for AuthWampCra (#992)
  fix: make run() of multiple components work on Windows (#986)
  new: max_retries now defaults to -1 ("try forever")