These are the commands I ran:
git clone https://github.com/vyos/vyos-build --branch crux
cd vyos-build/
docker build -t vyos-builder docker
This is the error message I got:
Get:1 http://deb.debian.org jessie-updates/main amd64 Packages [20 B]
Get:2 http://deb.debian.org jessie/main amd64 Packages [9,098 kB]
Get:3 http://security.debian.org jessie/updates/main amd64 Packages [918 kB]
Fetched 10.0 MB in 11s (856 kB/s)
W: Failed to fetch http://dev.packages.vyos.net/repositories/current/debian/dists/current/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
The command '/bin/sh -c apt-get update && apt-get install -y libyang-dev libyang0.16 chrpath install-in fo libjson-c-dev libpython3-dev python3-dev python3-pytest texinfo' returned a non-zero code: 100