copr_bug: APIv3 migration fixups
    
    See #458
    
    This feature couldn't have worked for a long time. According to the
    https://fedora-copr.github.io/posts/EOL-APIv1-APIv2
    the APIv1 code from copr-frontend was planned for September 2021 and
    was in fact removed during the 2021-10-01 release.
    https://docs.pagure.org/copr.copr/release-notes/2021-10-01.html#all-apiv1-code-removed