What is the relationship between the policy and policy-sources packages?
The policy package is a requirement for a working SELinux installation, while policy-sources is required if you want to customize the default policy. The policy package has the minimum files necessary for defining the SELinux security policy. It is kept trimmed down in size to support a minimal install footprint. The policy-sources package contains the source definitions in /etc/security/selinux/src that are required to create the files /etc/security/selinux/file_contexts and /etc/security/selinux/policy.