ppmquant --version (return code: 0)
ppmquant: Using libpbm from Netpbm Version: Netpbm 10.0
ppmquant: BSD defined
ppmquant: RGB_ENV='RGBDEF'
ppmquant: RGBENV= 'RGBDEF' (env vbl is unset)
ppmquant -HELP (return code: 1)
ppmquant: You must specify the number of colors in the output as an argument, or specify the -mapfile option.