PEP 524 has been implemented for 3.6b1 in #27776, so os.urandom() itself will now do the right thing for cryptographic use cases on Linux.

Accordingly, marking this as out of date - with os.urandom() and the secrets module both implicitly doing the right thing, the vagaries of operating system cryptographic RNG access can be left as obscure arcana of interest only to language runtime developers, rather than regular Python users :)