Downloading http://mirror.yandex.ru/debian/dists/stretch/InRelease...
Downloading http://mirror.yandex.ru/debian/dists/stretch/Release...
Downloading http://mirror.yandex.ru/debian/dists/stretch/Release.gpg...
openpgp:  RSA key ID 7638D0442B90D010
openpgp: Good signature from "Debian Archive Automatic Signing Key (8/jessie) <ftpmaster@debian.org>"
openpgp:  RSA key ID 04EE7237B7D453EC
openpgp: Good signature from "Debian Archive Automatic Signing Key (9/stretch) <ftpmaster@debian.org>"

Mirror [mirror11]: http://mirror.yandex.ru/debian/ stretch successfully added.
You can run 'aptly mirror update mirror11' to download repository contents.