After setting up a fresh ec2 instance, I tried to install vim using yum... I got this error:
ERROR: can not find RHNS CA file: /usr/share/rhn/RHN-ORG-TRUSTED-SSL-CERT
In the folder /usr/share/rhn/ the cert file is named wrong... you can simply make a copy of the cert with the correct name
(as root)
cd /usr/share/rhn/
cp RHNS-CA-CERT RHN-ORG-TRUSTED-SSL-CERT
This answer worked for me.
rvm autolibs read-only
In that way rvm do not try to download the dependencies from redhat. But it tell us what is missing, so we can install what is missing manually with yum install from centos repository.