pluralize() produces wrong plural for words ending in "x"

pluralize() produces wrong plural for words ending in "x": a task in Repo2RLEnv R2E-Gym / SWEGEN (Harbor dataset). The pluralize() function from boltons.strutils correctly adds "-es" for words ending in "s", "ch", or "sh", but it misses words ending in "x". Instead of producing "boxes", "foxes"…

The task

The `pluralize()` function from `boltons.strutils` correctly adds "-es" for words ending in "s", "ch", or "sh", but it misses words ending in "x". Instead of producing "boxes", "foxes", "taxes", etc., it appends a bare "s" and produces nonsense like "boxs", "foxs", "taxs".

Part of FineEnvs/repo2rlenv-r2e-gym.