Disable tests_rng on KVM

While working on reproducible builds for openSUSE, I found that building our python-autobahn package in a 1-core VM with

osc checkout openSUSE:Factory/python-autobahn && cd $_
osc build --noservice -j1 --vm-type=kvm

gets stuck forever in test_rng.py

[   73s] autobahn/rawsocket/test/test_rawsocket_url.py::TestParseWsUrl::test_parse_url16 PASSED [  8%]
[   73s] autobahn/rawsocket/test/test_rawsocket_url.py::TestParseWsUrl::test_parse_url17 PASSED [  8%]
[   73s] autobahn/rawsocket/test/test_rawsocket_url.py::TestParseWsUrl::test_parse_url18 PASSED [  8%]
[  238s] autobahn/test/test_rng.py::TestEntropy::test_depleting
[  238s]

[oberstet]

fixed via https://github.com/crossbario/autobahn-python/pull/1292

rng depletion tests are now skipped unless an env var AUTOBAHN_CI_ENABLE_RNG_DEPLETION_TESTS is set (to an arbitrary value).

in our CI, we do set this env var in tox: https://github.com/crossbario/autobahn-python/blob/master/tox.ini#L80 - that is, the RNG tests are still run on Travis and locally

[yan12125]

Could there be an environment variable that disables both depleting and non-depleting tests? if I understand https://github.com/crossbario/autobahn-python/issues/1275#issuecomment-568179899 correctly, the non-depleting test works correctly only if the depleting test is run first.

Use it at your own risk or use it with a hardware based random number generator with the rng-tools

Yep I switched to rng-tools later. It also makes the depleting test finish in a few seconds on my physical server. Not sure if it works on virtual machines or not, though, as it uses hardware random number generators.