python.pkgs.numtraits: move expression

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

···
+{ lib
+, buildPythonPackage
+, fetchPypi
+, pytest
+, six
+, numpy
+, traitlets
+}:
+
+buildPythonPackage rec {
+  pname = "numtraits";
+  version = "0.2";
+  name = "${pname}-${version}";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "2fca9a6c9334f7358ef1a3e2e64ccaa6a479fc99fc096910e0d5fbe8edcdfd7e";
+  };
+
+  checkInputs = [ pytest ];
+  propagatedBuildInputs = [ six numpy traitlets];
+
+  checkPhase = ''
+    py.test
+  '';
+
+  meta = {
+    description = "Numerical traits for Python objects";
+    license = lib.licenses.bsd2;
+    maintainers = with lib.maintainers; [ fridh ];
+    homepage = https://github.com/astrofrog/numtraits;
+  };
+}

pkgs/top-level/python-packages.nix

···
 
   numpy-stl = callPackage ../development/python-modules/numpy-stl { };
 
-  numtraits = buildPythonPackage rec {
-    pname = "numtraits";
-    version = "0.2";
-    name = "${pname}-${version}";
-
-    src = pkgs.fetchurl {
-      url = "mirror://pypi/${builtins.substring 0 1 pname}/${pname}/${name}.tar.gz";
-      sha256 = "2fca9a6c9334f7358ef1a3e2e64ccaa6a479fc99fc096910e0d5fbe8edcdfd7e";
-    };
-
-    buildInputs = with self; [ pytest ];
-    propagatedBuildInputs = with self; [ six numpy traitlets];
-
-    checkPhase = ''
-      py.test
-    '';
-
-    meta = {
-      description = "Numerical traits for Python objects";
-      license = licenses.bsd2;
-      maintainers = with maintainers; [ fridh ];
-      homepage = https://github.com/astrofrog/numtraits;
-    };
-  };
+  numtraits = callPackage ../development/python-modules/numtraits { };
 
   nwdiag = buildPythonPackage rec {
     name = "nwdiag-1.0.3";