docker: invalid reference format: repository name must be lowercase.

[gitmujoshi]

I am trying to follow along with Lynda class DevSecOps: Automated Security Testing but when I try to run gauntlt-docker eg. get "docker:invalid reference format: repository name must be lowercase"

bash-3.2$ gauntlt-docker --help
docker: invalid reference format: repository name must be lowercase.
See 'docker run --help'.