Fails to connect when port 8883 is closed

[mwfarb]

• We could try and catch this error, probe the port to provide a better error message.
• Using eduroam VPN on campus is enough to replicate and attempt to connect to a scene. It filters all ports but 80, 443.
• This is not useful:

Traceback (most recent call last):
  File "/Users/mwfarb/git/arena-py/tools/arb/arb.py", line 1394, in <module>
    scene = Scene(
  File "/Users/mwfarb/git/arena-py/arena/scene.py", line 179, in __init__
    self.mqttc.connect(self.host, port=8883)
  File "/usr/local/lib/python3.9/site-packages/paho/mqtt/client.py", line 937, in connect
    return self.reconnect()
  File "/usr/local/lib/python3.9/site-packages/paho/mqtt/client.py", line 1071, in reconnect
    sock = self._create_socket_connection()
  File "/usr/local/lib/python3.9/site-packages/paho/mqtt/client.py", line 3522, in _create_socket_connection
    return socket.create_connection(addr, source_address=source, timeout=self._keepalive)
  File "/usr/local/Cellar/python@3.9/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/socket.py", line 843, in create_connection
    raise err
  File "/usr/local/Cellar/python@3.9/3.9.5/Frameworks/Python.framework/Versions/3.9/lib/python3.9/socket.py", line 831, in create_connection
    sock.connect(sa)
socket.timeout: timed out
sys:1: RuntimeWarning: coroutine 'PersistentWorker.run' was never awaited
sys:1: RuntimeWarning: coroutine 'AsyncWorker.run' was never awaited