"undefined method `[]' for nil:NilClass" error when attempting to update packages in Puppet Enterprise 2015.2.0 to 2016.4.7, and 2016.5.1 to 2017.2.3

On any node, the Puppet agent returns undefined method `[]' for nil:NilClass errors when the enabled_repos_upload yum plugin is enabled and you are using ensure => latest with a package resource to...