nearblack --version (return code: 0)
GDAL 2.2.1, released 2017/06/23
nearblack -HELP (return code: 1)
nearblack [-of format] [-white | [-color c1,c2,c3...cn]*] [-near dist] [-nb non_black_pixels]
[-setalpha] [-setmask] [-o outfile] [-q] [-co "NAME=VALUE"]* infile