Building my own omnibus package and problems with bin/omnibus build gitlab

I have forked the gitlab-ce project and want to make my own omnibus package.My working environment is Centos 7 which is just installed.I followed the https://gitlab.com/gitlab-org/omnibus-gitlab/tree/master/doc/build step by step. Everything seems fine until I ran the command "bin/omnibus build gitlab".Here is the output:

It seems that it attempts to download the "readline" dependency but fails.Why does it try to access "172.22.8.106"?This ip address seems unreachable.