Added "python-$version-wrapper" expression.

The python wrapper expression expects a list of Python modules, $extraLibs,
which are added to $PYTHONPATH before executing the actual Python interpreter.

svn path=/nixpkgs/trunk/; revision=23194

pkgs/development/interpreters/python/wrapper.nix

@@ -0,0 +1,19 @@
+{stdenv, python, makeWrapper, extraLibs ? []}:
+
+stdenv.mkDerivation {
+  name = "python-${python.version}-wrapper";
+
+  propagatedBuildInputs = [python makeWrapper] ++ extraLibs;
+
+  unpackPhase = "true";
+  installPhase = ''
+    ensureDir "$out/bin"
+    declare -p
+    for prg in 2to3 idle pydoc python python-config python${python.majorVersion} python${python.majorVersion}-config smtpd.py; do
+      makeWrapper "$python/bin/$prg" "$out/bin/$prg" --set PYTHONPATH "$PYTHONPATH"
+    done
+  '';
+
+  inherit python;
+  inherit (python) meta;
+}