scons: Add passthru.py2 for backward compatibility

Not all packages build with Python 3, see #75877. The goal is to get rid
of Python 2 but this approach ensures a smoother transition.

pkgs/development/tools/build-managers/scons/common.nix

@@ -1,6 +1,6 @@
 { version, sha256 }:
 
-{ stdenv, fetchurl, python3Packages }:
+{ stdenv, fetchurl, python3Packages, python2Packages, scons }:
 
 python3Packages.buildPythonApplication rec {
   pname = "scons";
@@ -13,10 +13,10 @@ python3Packages.buildPythonApplication rec {
 
   setupHook = ./setup-hook.sh;
 
+  passthru.py2 = scons.override { python3Packages = python2Packages; };
+
   meta = with stdenv.lib; {
-    homepage = http://scons.org/;
     description = "An improved, cross-platform substitute for Make";
-    license = licenses.mit;
     longDescription = ''
       SCons is an Open Source software construction tool. Think of
       SCons as an improved, cross-platform substitute for the classic
@@ -25,6 +25,9 @@ python3Packages.buildPythonApplication rec {
       SCons is an easier, more reliable and faster way to build
       software.
     '';
+    homepage = "https://scons.org/";
+    changelog = "https://raw.githubusercontent.com/SConsProject/scons/rel_${version}/src/CHANGES.txt";
+    license = licenses.mit;
     platforms = platforms.all;
     maintainers = [ maintainers.primeos ];
   };

pkgs/development/tools/build-managers/scons/default.nix

@@ -1,12 +1,12 @@
-{ callPackage }:
+{ callPackage, python2Packages }:
 
 let
   mkScons = args: callPackage (import ./common.nix args) { };
 in {
-  scons_3_0_1 = mkScons {
+  scons_3_0_1 = (mkScons {
     version = "3.0.1";
     sha256 = "0wzid419mlwqw9llrg8gsx4nkzhqy16m4m40r0xnh6cwscw5wir4";
-  };
+  }).override { python3Packages = python2Packages; };
   scons_latest = mkScons {
     version = "3.1.2";
     sha256 = "1yzq2gg9zwz9rvfn42v5jzl3g4qf1khhny6zfbi2hib55zvg60bq";