nix test failing

grep -Ei '\b(download|copy|nixos\.org|github\.com)\b'  fails on latest state but not locally.

```
copying path '/nix/store/fm1dwqb08lxr1gk02niyvb1j7v4181c0-source' from 'https://cache.nixos.org'...
downloading 'https://cache.nixos.org/nar/18y5qya0pl3f470f7zhcniy8vb4if8a22iwzd0fjy7725bbmmwas.nar.xz'...
```
is the root cause on CI.