yum update

Downloading Packages:
warning: rpmts_HdrFromFdno: Header V3 RSA/SHA1 Signature, key ID 4520afa9: NOKEY
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY.art.txt

The GPG keys listed for the "CentOS / Red Hat Enterprise Linux 6 - atomicrocketturtle.com" repository are already installed but they are not correct for this package.
Check that the correct key URLs are configured for this repository.

rpm -q --queryformat "%{SUMMARY}n" gpg-pubkey

gpg(CentOS-6 Key (CentOS 6 Official Signing Key) <centos-6-key@centos.org>)
gpg(EPEL (6) <epel@fedoraproject.org>)
gpg(Atomic Rocket Turtle <admin@atomicrocketturtle.com>)
gpg(New Relic <support@newrelic.com>)

wget https://www.atomicorp.com/RPM-GPG-KEY.atomicorp.txt
mv RPM-GPG-KEY.atomicorp.txt /etc/pki/rpm-gpg/RPM-GPG-KEY.atomicorp.txt
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY.atomicorp.txt

gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY.art.txt

gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY.art.txt
        file:///etc/pki/rpm-gpg/RPM-GPG-KEY.atomicorp.txt

rpm -q --queryformat "%{SUMMARY}n" gpg-pubkey

rpm -import RPM-GPG-KEY.art.txt >/dev/null 2>&1

wget http://updates.atomicorp.com/channels/atomic/centos/7/x86_64/repodata/repomd.xml.key

sudo rpm --import repomd.xml.key