i am trying to make the environment to build my own flight controllers, for this purpose i have followed the path has been released on the http://ardupilot.org/dev/docs/building-setup-linux.html and then
i run this : Tools/scripts/install-prereqs-ubuntu.sh -y
Reading package lists… Done
W: http://ppa.launchpad.net/qgroundcontrol/ppa/ubuntu/dists/trusty/InRelease: Signature by key 1F476BD056310F007654224329AC9EC4FE821663 uses weak digest algorithm (SHA1)
W: The repository ‘http://ppa.launchpad.net/qgroundcontrol/ppa/ubuntu xenial Release’ does not have a Release file.
N: Data from such a repository can’t be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/qgroundcontrol/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
thank you for your help.