python-compat: adapt to Python 3.11 BC breakage with `random.sample`

As per https://docs.python.org/3/whatsnew/3.11.html#porting-to-python-3-11:

"The population parameter of `random.sample()` must be a sequence, and
automatic conversion of sets to lists is no longer supported.
Also, if the sample size is larger than the population size,
a `ValueError` is raised"
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