Note: help and version output are generated by a naïve script which tries a few variants of
<command> --help, <command> -h etc. to find the command's help and version info.
Sometimes it gets lucky, sometimes it doesn't; if the output below looks wrong, it probably is.
rgb2pct.py --version (return code: 0)
GDAL 2.2.1, released 2017/06/23
rgb2pct.py --help (return code: 1)
Usage: rgb2pct.py [-n colors | -pct palette_file] [-of format] source_file dest_file