in configuration.nix to override this.

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
         { allowUnsupportedSystem = true; }
       to ~/.config/nixpkgs/config.nix.

Cannot nix-instantiate `python3Packages.sipsimple.passthru.tests` because:
evaluation warning: 'sipsimple' has been renamed to 'python3-sipsimple' to fit upstream naming
error: attribute 'tests' in selection path 'python3Packages.sipsimple.passthru.tests' not found