The version of redhat-rpm-config currently in Fedora 27 includes some new convenience macros to make it easier to package projects hosted in Git repositories. See https://fedoraproject.org/wiki/Forge-hosted_projects_packaging_automation for details.
If I try to build such a package in Copr, I get the following error:
stderr: error: line 3: Unknown tag: %forgemeta
I guess the builders will need updating to allow this feature to be used.
I have updated the builder images and they now should contain the latest redhat-rpm-config package. It will take some time though until you get a new upgraded builder allocated because they will be now slowly replacing the previous old builders (I would like to avoid killing the current builders at the moment). If you are lucky, you can get a new builder even now but I would recommend waiting just a few hours.