openslide: Convert to new overlay system

pkgs/openslide/python.nix

@@ -0,0 +1,34 @@
+{ lib, fetchFromGitHub
+, python27Packages, openslide }:
+
+python27Packages.buildPythonPackage rec {
+  version = "1.1.1";
+  name = "openslide-python-${version}";
+
+  src = fetchFromGitHub {
+    owner = "openslide";
+    repo = "openslide-python";
+    rev = "v${version}";
+    sha256 = "1is8g8vy8s1xgfw8q76gdx8ygwvj56cl0vxfd3lx0iys15wzs7a4";
+  };
+
+  patches = [ ./zero-size-test-skip.patch ];
+
+  postPatch = ''
+    sed -i 's|LoadLibrary('\'''libopenslide.so.0'\''')|LoadLibrary('\'''${openslide}/lib/libopenslide.so.0'\''')|' openslide/lowlevel.py
+  '';
+
+  buildInputs = [
+    openslide
+  ];
+
+  propagatedBuildInputs = [
+    python27Packages.pillow
+  ];
+
+  meta = with lib; {
+    homepage = "http://openslide.org";
+    description = "Python bindings for OpenSlide.";
+    license = licenses.lgpl2;
+  };
+}