Code to reproduce problem:

population = list(range(10))
weights = list(-1 * w for w in range(10))
[random.choices(population, weights) for _ in range(1000)]

will raise IndexError:

    358         bisect = _bisect.bisect
    359         total = cum_weights[-1]
--> 360         return [population[bisect(cum_weights, random() * total)] for i in range(k)]
    361 
    362 ## -------------------- real-valued distributions  -------------------

IndexError: list index out of range