python2Packages.packaging: keep 20.4 around

pkgs/development/python-modules/packaging/2.nix

@@ -0,0 +1,40 @@
+{ stdenv
+, buildPythonPackage
+, fetchPypi
+, pyparsing
+, six
+, pytestCheckHook
+, pretend
+, flit-core
+}:
+
+# We keep 20.4 because it uses setuptools instead of flit-core
+# which requires Python 3 to build a universal wheel.
+
+buildPythonPackage rec {
+  pname = "packaging";
+  version = "20.4";
+  format = "setuptools";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "4357f74f47b9c12db93624a82154e9b120fa8293699949152b22065d556079f8";
+  };
+
+  propagatedBuildInputs = [ pyparsing six ];
+
+  checkInputs = [
+    pytestCheckHook
+    pretend
+  ];
+
+  # Prevent circular dependency
+  doCheck = false;
+
+  meta = with stdenv.lib; {
+    description = "Core utilities for Python packages";
+    homepage = "https://github.com/pypa/packaging";
+    license = [ licenses.bsd2 licenses.asl20 ];
+    maintainers = with maintainers; [ bennofs ];
+  };
+}

pkgs/top-level/python-packages.nix

@@ -4348,7 +4348,9 @@ in {
 
   oyaml = callPackage ../development/python-modules/oyaml { };
 
-  packaging = callPackage ../development/python-modules/packaging { };
+  packaging = if isPy3k
+    then callPackage ../development/python-modules/packaging { }
+    else callPackage ../development/python-modules/packaging/2.nix { };
 
   packet-python = callPackage ../development/python-modules/packet-python { };