Log show 'Error : nothing to do' with yum install ranger_2_3_*-admin'.
I also check with : yum list| grep 'ranger*'
Only plugins are there no admin package found.
Which instance are you using? Sandbox or AWS practice instance?
Install Ranger is part of the exam requirement. I had tried multiple times before I did the exam. I was able to install in both Sandbox and AWS instances.
You can try to download the latest Sandbox and give a go.
I am using Sandbox, it is having HDP version 2.3.0. It might work with latest sandbox.
My Sandbox is v2.6.4. The latest version from Hortonwork is also v2.6.4.
It works for Ranger installation.