pythonPackages: Add version and pname attributes to packages

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

@@ -5,8 +5,9 @@
 , python
 }:
 buildPythonPackage rec {
-  name = "cymem-${version}";
+  pname = "cymem";
   version = "1.31.2";
+  name = pname + "-" + version;
 
   src = fetchFromGitHub {
     owner = "explosion";
@@ -16,14 +17,14 @@ buildPythonPackage rec {
   };
 
   propagatedBuildInputs = [
-   cython   
+   cython
   ];
-    
+
   checkPhase = ''
     cd cymem/tests
     ${python.interpreter} -m unittest discover -p "*test*"
   '';
-  
+
   meta = with stdenv.lib; {
     description = "Cython memory pool for RAII-style memory management";
     homepage = https://github.com/explosion/cymem;