OSX doesn't always have sched_getaffinity

[Wirick]

1. The python client breaks when calling
   CPU_COUNT: int = len(os.sched_getaffinity(0))

What this PR does / why we need it:
When importing the python client I encounter an error

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'os' has no attribute 'sched_getaffinity'

We should fallback or use another trick to compute this value, it seems to be a known issue
https://stackoverflow.com/questions/42538153/python-3-6-0-os-module-does-not-have-sched-getaffinity-method

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[mrzzy]

@Wirick Thanks for this. However, this seems to be a duplicate of #839?

[Wirick]

didn't even see it just fixed in the dev process