Package: ftp.debian.org src:rfc5766-turn-server is replaced by the new src:coturn
Upstream explain it here: https://github.com/coturn/coturn/wiki/NEWS#version-3300 "Project copied from rfc5766-turn-server trunk." The new source package is here: https://packages.qa.debian.org/c/coturn.html and it is now available in jessie, stretch and sid
