Docs: setup HW entropy for TLS

Sometimes at boot time happens this error in connection to crossbar (wss://). But after boot if I try to restart my service, it works fine.

Autobahn v18.10.1
Python 3.5.3

2018-11-22 16:10:41.398 474 INFO autobahn.asyncio.component.Component [-] connecting once using transport type "websocket" over endpoint "tcp"
2018-11-22 16:10:41.408 474 ERROR asyncio [-] Fatal error on SSL transport
protocol: <asyncio.sslproto.SSLProtocol object at 0x755234f0>
transport: <_SelectorSocketTransport closing fd=8 read=idle write=<idle, bufsize=0>>: ssl.SSLError: getrandom() initialization failed. (_ssl.c:720)
2018-11-22 16:10:41.408 474 ERROR asyncio Traceback (most recent call last):
2018-11-22 16:10:41.408 474 ERROR asyncio   File "/usr/lib/python3.5/asyncio/sslproto.py", line 635, in _process_write_backlog
2018-11-22 16:10:41.408 474 ERROR asyncio     self._on_handshake_complete)
2018-11-22 16:10:41.408 474 ERROR asyncio   File "/usr/lib/python3.5/asyncio/sslproto.py", line 135, in do_handshake
2018-11-22 16:10:41.408 474 ERROR asyncio     ssldata, appdata = self.feed_ssldata(b'', only_handshake=True)
2018-11-22 16:10:41.408 474 ERROR asyncio   File "/usr/lib/python3.5/asyncio/sslproto.py", line 201, in feed_ssldata
2018-11-22 16:10:41.408 474 ERROR asyncio     self._sslobj.do_handshake()
2018-11-22 16:10:41.408 474 ERROR asyncio   File "/usr/lib/python3.5/ssl.py", line 641, in do_handshake
2018-11-22 16:10:41.408 474 ERROR asyncio     self._sslobj.do_handshake()
2018-11-22 16:10:41.408 474 ERROR asyncio ssl.SSLError: getrandom() initialization failed. (_ssl.c:720)
2018-11-22 16:10:41.408 474 ERROR asyncio
2018-11-22 16:10:41.418 474 INFO autobahn.asyncio.component.Component [-] Connection failed: SSLError: getrandom() initialization failed. (_ssl.c:720)

Any suggestion?

The issue names no file or test. Start from the reported Python 3.5 SSL/TLS error during boot and determine the hardware-entropy setup guidance needed; done means documenting a clear setup that prevents the getrandom() initialization failure.