Nick: "+1 for a fallback in the SIPHash initialisation as well."

Sorry but I don't know a simple function to implement this. We might use the LCG RNG, but it's not really designed to be "secure". I don't think that it makes sense to initialize a shiny SIPHash with a crappy LCG RNG :-)

So I skip my turn on this idea and let others implement them if anyone consider that it's worth it.

To be clear: Python 3 doesn't start when getrandom() and /dev/urandom are not available or don't work, but it's not something new. Python 3.1 already starts with:

    fd = open("/dev/urandom", O_RDONLY);
    if (fd < 0)
        Py_FatalError("Failed to open /dev/urandom");

--

os.urandom() is now blocking, I close the issue.