[Python] Autobahn websocket issue while running with twistd using tac file

I have a WebSocket server implemented using autobahn WebSocket framework using twisted. WebSocket server runs fine when the program ran with python. But if I run this using twistd server runner by creating tac file as twisted service, I get the following error in server while any client try to establish connection and the handshake is failing.

2015-12-08 07:17:56,022 - CRITICAL - twisted.publishToNewObserver() 154 Unhandled Error
Traceback (most recent call last):
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/twisted/python/log.py", line 84, in callWithContext
return context.call({ILogContext: newCtx}, func, *args, **kw)
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/twisted/python/context.py", line 118, in callWithContext
return self.currentContext().callWithContext(ctx, func, *args, **kw)
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/twisted/python/context.py", line 81, in callWithContext
return func(*args,**kw)
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/twisted/internet/posixbase.py", line 597, in _doReadOrWrite
why = selectable.doRead()
--- <exception caught here> ---
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/twisted/internet/tcp.py", line 1067, in doRead
protocol = self.factory.buildProtocol(self._buildAddr(addr))
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/twisted/internet/protocol.py", line 135, in buildProtocol
p = self.protocol()
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/autobahn/websocket/protocol.py", line 665, in __init__
self.is_closed = txaio.create_future()
File "/opt/nrgi-ws/nrgi-ws-virtual-env/local/lib/python2.7/site-packages/txaio/_unframework.py", line 43, in _throw_usage_error
"To use txaio, you must first select a framework "
exceptions.RuntimeError: To use txaio, you must first select a framework with .use_twisted() or .use_txaio()

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