$ nix-build travis.nix -A build --substituters https://nixcache.reflex-frp.org/ --trusted-public-keys ryantrinkle.com-1:JJiAKaRv9mWgpVAz8dwewnZe0AzzEAzPkagE9SP5NWI=
warning: ignoring untrusted substituter 'https://nixcache.reflex-frp.org/'
warning: ignoring the user-specified setting 'trusted-public-keys', because it is a restricted setting and you are not a trusted user