update print_image fatal error message
update print_image fatal error message

sys.exc_info is generally not super helpful in debugging a failure in pcv.print_image. Instead, replace it with information that type(img) is not compatible.

stiphyMT/plantcv,stiphyMT/plantcv,danforthcenter/plantcv,danforthcenter/plantcv,danforthcenter/plantcv,stiphyMT/plantcv