python.pkgs.vine: move to separate expression

pkgs/development/python-modules/vine/default.nix

@@ -0,0 +1,23 @@
+{ stdenv, buildPythonPackage, fetchPypi
+, case, pytest, pythonOlder }:
+
+buildPythonPackage rec {
+  pname = "vine";
+  version = "1.1.3";
+  name = "${pname}-${version}";
+
+  disable = pythonOlder "2.7";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "0h94x9mc9bspg23lb1f73h7smdzc39ps7z7sm0q38ds9jahmvfc7";
+  };
+
+  buildInputs = [ case pytest ];
+
+  meta = with stdenv.lib; {
+    description = "Python promises";
+    homepage = https://github.com/celery/vine;
+    license = licenses.bsd3;
+  };
+}