Given following log snippets, their explanation, and nothing else, explain what failure, if any, occurred during build of this package.

  Snippets are in a format of [X] : [Y], where [X] is a log snippet, and [Y] is the explanation.

  Snippets are delimited with '================'.

  Drawing on information from all snippets, provide a concise explanation of the issue and recommend a solution.

  Explanation of the issue, and recommended solution, should take a handful of sentences.

  Snippets:

  [           {'baseurl': 'https://download.copr.fedorainfracloud.org/results/plautrba/selinux-fedora/fedora-$releasever-$basearch/',
            'id': 'https_download_copr_fedorainfracloud_org_results_plautrba_selinux_fedora_fedora_releasever_basearch',
            'name': 'Additional repo '
                    'https_download_copr_fedorainfracloud_org_results_plautrba_selinux_fedora_fedora_releasever_basearch'}],]: [This part of the task JSON tells you that there's an external (additional) repository used during package build. Copr consumes RPMs from multiple sources, and this one is non-standard.]
=============
[99.86.229.6)
Error: Failed to download metadata for repo 'https_download_copr_fedorainfracloud_org_results_plautrba_selinux_fedora_fedora_releasever_basearch': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried
ERROR: Exception(/var/lib/copr-rpmbuild/workspace/workdir-x79ufehf/policycoreutils/policycoreutils.spec) Config(fedora-rawhide-x86_64) 0 minutes 25 seconds
INFO: Results and/or logs in: /var/lib/copr-rpmbuild/results
INFO: Cleaning up build root ('cleanup_on_failure=True')
Start: clean chroot
Finish: clean chroot
ERROR: Command failed: 
 # /usr/bin/systemd-nspawn -q -M 30]: [But since DNF (called by Mock in the background) doesn't see the repository (error 404), it seems that the repository was not specified properly.

Namely, in this case, we are building for `fedora-rawhide-repository` but the repo was specified for `fedora-40-repository`.  Rawhide, at the time of build, was really F40, but Copr doesn't know how to expand `$releasever` to `rawhide`.]

Issue: Improperly specified external repository.
Resolution: Try to use `$chroot` in your external repository specification, or, if it is an external repo, use `copr://owner/repo`.