Revert "Downgrade to Python to 3.9 on macOS Nix"

This reverts commit c965f04.

.github/workflows/python-package.yml

@@ -46,12 +46,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        include:
-          - os: ubuntu-latest
-            python-version: python310
-          - os: macos-latest
-            python-version: python39
-            # see https://github.com/cachix/install-nix-action/issues/135
+        os:
+          - ubuntu-latest
+          - macos-latest
     needs:
       - build-wheel
     steps:
@@ -65,7 +62,6 @@ jobs:
         run: |
           nix-shell \
             --pure \
-            --argstr pythonVersion ${{ matrix.python-version }} \
             --run '
               python -m venv venv
               source venv/bin/activate

default.nix

@@ -1,7 +1,7 @@
-{ pkgs ? import <nixpkgs> { }, pythonVersion ? "python311" }:
+{ pkgs ? import <nixpkgs> { } }:
 (
   pkgs.stdenv.mkDerivation {
     name = "darker-test";
-    buildInputs = [ pkgs.${pythonVersion} pkgs.git ];
+    buildInputs = [ pkgs.python310 pkgs.git ];
   }
 )