start_fails_if_transport_fails_when_receiving_messages tests failing on Linux

[moozzyk]

connection_impl_start.start_fails_if_transport_fails_when_receiving_messages is consistently failing on Linux.

It looks like the exception is being sliced somewhere. The tests asserts that starting the transport should write the following error message:
connection could not be started due to: receive error
the actual message is:
connection could not be started due to: std::exception

I reviewed the code and could not find any place where we could be slicing the exception. The same test works on Windows as expected so it might be an external, Linux specific issue

2015-12-11T06:02:52.453038Z [state change] disconnected -> connecting
2015-12-11T06:02:52.45857Z [info        ] [websocket transport] connecting to: ws://start_fails_if_transport_fails_when_receiving_messages/connect?transport=webSockets&clientProtocol=1.4&connectionToken=A==
2015-12-11T06:02:52.459323Z [error       ] [websocket transport] error receiving response from websocket: receive error
2015-12-11T06:02:52.459473Z [info        ] connection lost - trying to re-establish connection
2015-12-11T06:02:52.459495Z [info        ] acquired lock before invoking reconnecting callback
2015-12-11T06:02:52.459808Z [error       ] connection could not be started due to: std::exception
2015-12-11T06:02:52.45985Z [state change] connecting -> disconnected