Gem File missing

Hello everyone !,

So I’m using gitlab-ce as a docker container, such as the gitlab runner on a CentOS server. I was havin some problems with DNS, but I’ve figured out, granting firewall permission to docker network. But another problem has appeared, that is this as it shows on this link:

Error

Edit: This is the gitlab-ci.yml that I’m using: gitlab-ci.yml

I don’t have much experience workin with gitlab and I have no idea what this Gemfile is. Thanks in advance for anyone who can help me.