SELinux bindings not found.

Puppet Version: 5.5.2
Puppet Server Version: 2018.1.0.54
OS Name/Version: RedHat 7.5

After a fresh install of the O/S, and installation of Puppet Enterprise 2018.1.2, I'm now seeing the following error messages:

Debug: /Stage[main]/Gcssj::Configuration::Files/File[/var/gcssj]/seltype: SELinux bindings not found. Ignoring parameter.

After searching for some time, I found that this apparently refers to not having the SELinux Ruby bindings installed.  So I installed 'libselinux-ruby' (version 2.5-12.el7, it was the only version available) from the DVD used to install the O/S.  Despite doing so on both the puppet server and the agent, and rebooting them, I'm still getting the same error message.

Please Note: It is not possible to simply add a remote repo to the system.  The system must install without any internet access.  The customer requires this.

Desired Behavior:

Puppet should be able to install itself without difficulty, and should be able to do so without having any additional repos available.  At the least, a complete list of all dependencies required for full support of all features, that are not included in the PE bundle, must be provided.

Actual Behavior:

Despite installing the apparently required package, puppet still fails with the same message.