facedetect: use Python 3

pkgs/tools/graphics/facedetect/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, python2Packages }:
+{ lib, stdenv, fetchFromGitHub, fetchpatch, python3Packages }:
 
 stdenv.mkDerivation rec {
   pname = "facedetect";
@@ -11,14 +11,22 @@ stdenv.mkDerivation rec {
     sha256 = "0mddh71cjbsngpvjli406ndi2x613y39ydgb8bi4z1jp063865sd";
   };
 
-  buildInputs = [ python2Packages.python python2Packages.wrapPython ];
-  pythonPath = [ python2Packages.numpy python2Packages.opencv4 ];
+  patches = [
+    (fetchpatch {
+      name = "python3-support.patch";
+      url = "https://gitlab.com/wavexx/facedetect/-/commit/8037d4406eb76dd5c106819f72c3562f8b255b5b.patch";
+      sha256 = "1752k37pbkigiwglx99ba9360ahzzrrb65a8d77k3xs4c3bcmk2p";
+    })
+  ];
+
+  buildInputs = [ python3Packages.python python3Packages.wrapPython ];
+  pythonPath = [ python3Packages.numpy python3Packages.opencv4 ];
 
   dontConfigure = true;
 
-  patchPhase = ''
+  postPatch = ''
     substituteInPlace facedetect \
-      --replace /usr/share/opencv "${python2Packages.opencv4}/share/opencv4"
+      --replace /usr/share/opencv "${python3Packages.opencv4}/share/opencv4"
   '';
 
   installPhase = ''