partially fix pythonPackages.protobuf

pkgs/development/libraries/protobuf/2.5.nix

@@ -2,6 +2,7 @@
 
 callPackage ./generic.nix (args // rec {
   version = "2.5.0";
+  # make sure you test also -A pythonPackages.protobuf
   src = fetchurl {
     url = "http://protobuf.googlecode.com/files/${version}.tar.bz2";
     sha256 = "0xxn9gxhvsgzz2sgmihzf6pf75clr05mqj6218camwrwajpcbgqk";

pkgs/development/libraries/protobuf/2.6.nix

@@ -2,6 +2,7 @@
 
 callPackage ./generic.nix (args // rec {
   version = "2.6.1";
+  # make sure you test also -A pythonPackages.protobuf
   src = fetchFromGitHub {
     owner = "google";
     repo = "protobuf";

pkgs/development/libraries/protobuf/generic.nix

@@ -4,7 +4,7 @@
 }:
 
 stdenv.mkDerivation rec {
-  name = "protobuf-${version}";
+  name = "protobuf-v${version}";
 
   inherit src;
 

pkgs/top-level/python-packages.nix

@@ -7489,9 +7489,8 @@ let
   protobuf = buildPythonPackage rec {
     inherit (pkgs.protobuf) name src;
 
-    propagatedBuildInputs = with self; [ pkgs.protobuf google_apputils  ];
-    sourceRoot = "${name}/python";
-
+    propagatedBuildInputs = with self; [ pkgs.protobuf google_apputils ];
+    sourceRoot = "${name}-src/python";
 
     meta = {
       description = "Protocol Buffers are Google's data interchange format";