feat(shell.nix): Switch to python 3.9

shell.nix

@@ -1,29 +1,12 @@
-{ pkgs ? import <nixpkgs> { }, ... }:
+{
+  pkgs ? import <nixpkgs> { },
+  ...
+}:
 
 let
-  python = pkgs.python38;
-
-  django-types = python.pkgs.buildPythonPackage rec {
-    pname = "django-types";
-    version = "0.17.0";
-
-    format = "pyproject";
-
-    src = pkgs.fetchPypi {
-      inherit pname version;
-      hash = "sha256-wcQqt4h2xXxyg0LVqwYHJas3H8jcg7uFuuC+BoRqrXA=";
-    };
-
-    nativeBuildInputs = with python.pkgs; [ poetry-core ];
-
-    # setup.cfg tries to pull in nonexistent LICENSE.txt file
-    # postPatch = "rm setup.cfg";
-
-    # propagatedBuildInputs = [ django typing-extensions ];
-  };
+  python = pkgs.python39;
 in
 
-
 pkgs.mkShell {
   shellHook = ''
     export DJANGO_SETTINGS_MODULE=gestioasso.settings.local
@@ -34,11 +17,14 @@ pkgs.mkShell {
     pip install -r requirements-devel.txt | grep -v 'Requirement already satisfied:'
   '';
 
-  packages = [ python django-types ] ++ (with python.pkgs; [
-    pip
-    virtualenv
-    python-ldap
-  ]);
+  packages =
+    [ python ]
+    ++ (with python.pkgs; [
+      django-types
+      pip
+      virtualenv
+      python-ldap
+    ]);
 
   allowSubstitutes = false;
 }