{ nixpkgs }: let pkgs = import nixpkgs { system = "x86_64-linux"; overlays = [ ]; config = { checkMeta = true; problems.matchers = [ { package = "a"; handler = "error"; } ]; }; }; in pkgs.stdenvNoCC.mkDerivation { pname = "a"; version = "0"; meta.description = "Some package"; meta.problems.removal = { }; }