Get colorscheme.

def get(img, light=False):
    """Get colorscheme."""
    if not shutil.which("schemer2"):
        logging.error("Schemer2 wasn't found on your system.")
        logging.error("Try another backend. (wal --backend)")
        sys.exit(1)

    cols = [col.decode('UTF-8') for col in gen_colors(img)]
    return adjust(cols, light)