create derivation for notify-send.py

It's a more fully-featured client than libnotify's notify-send: we
don't need to install it but it's handly for testing the server

crier/notify-send.nix

@@ -0,0 +1,32 @@
+
+# notify-send.py is not needed for installation but it's
+# handy for testing, as it supports more features of the
+# notification protocol than the basic notify-send.
+#
+# https://wiki.archlinux.org/title/Desktop_notifications#Tips_and_tricks
+#
+# Getting it to build in nixpkgs was fun: it requires the
+# deprecated dbus-notify library, which doesn't play nice with
+# standard Python tooling
+
+{ pkgs, lib, dbus, fetchpatch, fetchFromGitHub, python38Packages }:
+
+python38Packages.buildPythonApplication rec {
+  pname = "notify-send";
+  version = "git";
+  format = "pyproject";
+  src = fetchFromGitHub {
+    owner = "phuhl";
+    repo = "notify-send.py";
+    rev = "0575c79f10d10892c41559dd3695346d16a8b184";
+    hash = "sha256:09m15h1yja5x2ihrp92ab3q220mgdcb0k4ld00dccn4krzcn3a7v";
+  };
+
+  patchPhase = ''
+    sed -i pyproject.toml -e 's/"dbus-python",//'
+  '';
+
+  propagatedBuildInputs = with python38Packages; [
+    dbus-python pygobject3 setuptools flit pip
+  ];
+}