Motivation for this change

Changelog: (3.1.0, 3.0.0)

Package changes

• Add docutils, because virt-manager now uses rst2man to generate man pages. I wasn't sure if the nativeBuildInputs is the correct place for docutils, but as far as I have tested, that's the only place where the build doesn't fail.

Notes

• virt-manager is now using pytest, so it might be easier to integrate tests. I haven't tried that though.
• I wasn't sure about the formatting of the file, so it might be incorrect.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.