Support __index__() in getrandbits(), randbytes() and others

[serhiy-storchaka]

Feature or enhancement

Support of the __index__() method in getrandbits() and randbytes() is inconsistent.

• Random.getrandbits() supports __index__(), but SystemRandom.getrandbits() does not.
• SystemRandom.randbytes() supports __index__(), but Random.randbytes() does not.

For consistence, both classes should support it.

sample() fails if its k argument is not integer. k should have __index__(), but it also should support comparison with integers and multiplication by list and integer. It is easy to make it more general, and only require __index__(). It will also produce more meaningful error.

binomialvariate() seems "working" with non-integer n argument, but the result is questionable. Passing non-integer value is most likely an error, and it would be better to detect it.

cc @rhettinger

[rhettinger]

Personally, I don't think this is needed. It is just overhead that doesn't benefit real users.

In pure python code, we commonly do much less error checking on inputs than we do in C code.