Hello,
we have just deployed a hotfix for *Bug 1550986* https://bugzilla.redhat.com/show_bug.cgi?id=1550986 - HTTPS Error 500 when trying to enable repository trough yum-plugin-copr on RHEL7, Centos 7. `yum copr enable` should work again.
COPR team
copr-devel@lists.fedorahosted.org