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"…