# cat ssh_user_enumeration.py
# python ssh_user_enumeration.py 127.0.0.1 22 user1 0
# python ssh_user_enumeration.py 127.0.0.1 22 user2 0
# python ssh_user_enumeration.py 127.0.0.1 22 root 3
# python ssh_user_enumeration.py 127.0.0.1 22 user3 3
Reference
http://seclists.org/fulldisclosure/2016/Jul/51