Try running a
yum update first. The
ovirt-release.noarch.rpm did not include a RPM key and it's now complaining that there is no signing key available in your RPM configuration that can be used to verify the authenticity of the
Poking around the ovirt website, I did find this page titled: oVirt Deployment Options. It discusses that the RPMs are signed, which is a good thing.
GPG Keys used by oVirt
Important: We are going to sign RPMs only from next release. Please wait for the announcement email
For starters I would attempt to do this first, to see if you can get
yum to do the heavy lifting and install the RPM keys for ovirt.
$ sudo yum install ovirt-release
If that doesn't resolve things then you'll likely need to follow the directions from the link above which has full details for importing the keys manually into your RPM installation using
If you'd just like to get past this whole thing you can of course tell
yum to disregard checking the origins of the packages like so:
$ yum -y --nogpgcheck install ovirt-engine