|   | 1 |  initial version  | 
if it is the same code from the dnn/samples folder (under another name ?), then it's indeed simple:
opencv's CommandLineParser expects arguments in --key=value fashion, you're missing the = ;)
in your case, it should be:
kpd -i=/home/brian/Pictures/MyPic/IMG20180801205312.jpg -m=pose_iter_440000.caffemodel -p=pose_deploy_linevec.prototxt