Downloading: http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/dists/stretch/InRelease
Error (retrying): HTTP code 404 while fetching http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/dists/stretch/InRelease
Retrying 0 http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/dists/stretch/InRelease...
Download Error: http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/dists/stretch/InRelease
Downloading: http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/dists/stretch/Release
Downloading: http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/dists/stretch/Release.gpg
openpgp:  RSA key ID 04EE7237B7D453EC
openpgp: Good signature from "Debian Archive Automatic Signing Key (9/stretch) <ftpmaster@debian.org>"
openpgp:  RSA key ID 648ACFD622F3D138
openpgp: Good signature from "Debian Archive Automatic Signing Key (10/buster) <ftpmaster@debian.org>"
openpgp:  RSA key ID 0E98404D386FA1D9
openpgp: Good signature from "Debian Archive Automatic Signing Key (11/bullseye) <ftpmaster@debian.org>"
openpgp:  RSA key ID EF0F382A1A7B6500
openpgp: Good signature from "Debian Stable Release Key (9/stretch) <debian-release@lists.debian.org>"

Mirror [mirror11]: http://repo.aptly.info/system-tests/archive.debian.org/debian-archive/debian/ stretch successfully added.
You can run 'aptly mirror update mirror11' to download repository contents.