NUR = {
      type = "github";
      owner = "nix-community";
      repo = "NUR";
      flake = false;
    };

error: while evaluating the attribute 'activationScript' of the derivation 'nixos-system-shelter-20.09.20200520.fa65afd'

while evaluating 'addContextFrom' at /nix/store/40r47v1ldrh6f7vvak81dd2fy1xsy1xw-source/lib/strings.nix:369:23, called from /nix/store/40r47v1ldrh6f7vvak81dd2fy1xsy1xw-source/lib/strings.nix:385:11:
while evaluating the attribute 'system' at /nix/store/40r47v1ldrh6f7vvak81dd2fy1xsy1xw-source/pkgs/top-level/impure.nix:89:25:
attribute 'currentSystem' missing, at /nix/store/40r47v1ldrh6f7vvak81dd2fy1xsy1xw-source/pkgs/top-level/impure.nix:89:34

$ nix build .#nixosConfigurations.silence.config.system.build.toplevel        
warning: flake ' git+file:///home/balsoft/projects/vyorkin/nixos-config?ref=master&rev=1c178bcafdd5bf6ffa8d62de4130f81bdac46f09 ' has deprecated attribute 'edition'
error: The option `libinput' defined in `/nix/store/q4k13fi5sxcvp42by77gx0pfwjvq5j4h-source/cfgs/x11/laptop.nix' does not exist.
(use '--show-trace' to show detailed location information)