pythonPackages.pygobject2: fixup conversation to buildPythonPackage

Changed files
+1
pkgs
development
python-modules
pygobject
+1
pkgs/development/python-modules/pygobject/default.nix
···
buildPythonPackage rec {
name = "pygobject-${version}";
version = "2.28.6";
+
format = "other";
src = fetchurl {
url = "mirror://gnome/sources/pygobject/2.28/${name}.tar.xz";