[issue30030] Simplify _RandomNameSequence

[STINNER Victor]

STINNER Victor added the comment:

> Remoe _get_candidate_names() and the global _name_sequence

I understood the rationale behind _get_candidate_names() is to prevent generating the same name when _RandomNameSequence() uses random.Random. Since my change uses random.SystemRandom, I consider that it's now ok to create multiple generators in paralle. Is that rationale correct?

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30030>
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