pywal: move to pythonPackages and inject path to convert

pkgs/development/python-modules/pywal/convert.patch

@@ -0,0 +1,21 @@
+diff --git a/pywal/backends/wal.py b/pywal/backends/wal.py
+index a75fdc5..4339680 100644
+--- a/pywal/backends/wal.py
++++ b/pywal/backends/wal.py
+@@ -21,15 +21,7 @@ def imagemagick(color_count, img, magick_command):
+
+ def has_im():
+     """Check to see if the user has im installed."""
+-    if shutil.which("magick"):
+-        return ["magick", "convert"]
+-
+-    if shutil.which("convert"):
+-        return ["convert"]
+-
+-    logging.error("Imagemagick wasn't found on your system.")
+-    logging.error("Try another backend. (wal --backend)")
+-    sys.exit(1)
++    return ["@convert@"]
+
+
+ def gen_colors(img):

pkgs/development/python-modules/pywal/default.nix

@@ -0,0 +1,36 @@
+{ lib, python3Packages, imagemagick, feh }:
+
+python3Packages.buildPythonApplication rec {
+  pname = "pywal";
+  version = "3.2.1";
+
+  src = python3Packages.fetchPypi {
+    inherit pname version;
+    sha256 = "1pj30h19ijwhmbm941yzbkgr19q06dhp9492h9nrqw1wfjfdbdic";
+  };
+
+  # necessary for imagemagick to be found during tests
+  buildInputs = [ imagemagick ];
+
+  makeWrapperArgs = [ "--prefix PATH : ${lib.makeBinPath [ imagemagick feh ]}" ];
+
+  preCheck = ''
+    mkdir tmp
+    HOME=$PWD/tmp
+  '';
+
+  patches = [
+    ./convert.patch
+  ];
+
+  postPatch = ''
+    substituteInPlace pywal/backends/wal.py --subst-var-by convert "${imagemagick}/bin/convert"
+  '';
+
+  meta = with lib; {
+    description = "Generate and change colorschemes on the fly. A 'wal' rewrite in Python 3.";
+    homepage = https://github.com/dylanaraps/pywal;
+    license = licenses.mit;
+    maintainers = with maintainers; [ Fresheyeball ];
+  };
+}