python future: add expression

pkgs/top-level/python-packages.nix

@@ -4284,6 +4284,39 @@ let
     };
   });
 
+  future = buildPythonPackage rec {
+    version = "v0.14.3";
+    name = "future-${version}";
+
+    src = pkgs.fetchurl {
+      url = "http://github.com/PythonCharmers/python-future/archive/${version}.tar.gz";
+      sha256 = "0hgp9kq7h4ipw8ax5xvvkyh3bkqw361d3rndvb9xix01h9j9mi3p";
+    };
+
+    propagatedBuildInputs = with self; optionals isPy26 [ importlib argparse ];
+    doCheck = false;
+
+    meta = with stdenv.lib; {
+      description = "Clean single-source support for Python 3 and 2";
+      longDescription = ''
+        python-future is the missing compatibility layer between Python 2 and
+        Python 3. It allows you to use a single, clean Python 3.x-compatible
+        codebase to support both Python 2 and Python 3 with minimal overhead.
+
+        It provides future and past packages with backports and forward ports
+        of features from Python 3 and 2. It also comes with futurize and
+        pasteurize, customized 2to3-based scripts that helps you to convert
+        either Py2 or Py3 code easily to support both Python 2 and 3 in a
+        single clean Py3-style codebase, module by module.
+      '';
+      homepage = https://python-future.org;
+      downloadPage = https://github.com/PythonCharmers/python-future/releases;
+      license = licenses.mit;
+      maintainers = with maintainers; [ prikhi ];
+      platforms = platforms.linux;
+    };
+  };
+
   futures = buildPythonPackage rec {
     name = "futures-2.1.6";