The update to puppet-agent-1.7.0-1.el7 failed because it was trying to update without the new release key having already been installed:
$ sudo yum update
puppet-agent x86_64 1.7.0-1.el7 puppetlabs-pc1 24 M
puppetlabs-release noarch 22.0-2 puppetlabs-products 14 k
puppetlabs-release-pc1 noarch 1.1.0-2.el7 puppetlabs-pc1 14 k
Is this ok [y/d/N]: y
warning: /var/cache/yum/x86_64/7/puppetlabs-pc1/packages/puppet-agent-1.7.0-1.el7.x86_64.rpm: Header V4 RSA/SHA1 Signature, key ID ef8d349f: NOKEY
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-puppetlabs-PC1
The GPG keys listed for the "Puppet Labs PC1 Repository el 7 - x86_64" repository are already installed but they are not correct for this package.
Check that the correct key URLs are configured for this repository.
Failing package is: puppet-agent-1.7.0-1.el7.x86_64
GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-puppetlabs-PC1
If I broke this down and updated the two release packages first, then the agent later, all was well and flowed smoothly. To me this would suggest that puppet-agent is missing a versioned dependency on one of those two newer release packages. With that in place, yum would just do the right thing automatically.