python.pkgs.argon2_cffi: add enum34 dependency

pkgs/development/python-modules/argon2_cffi/default.nix

@@ -1,30 +1,33 @@
 { cffi
 , six
+, enum34
 , hypothesis
 , pytest
 , wheel
 , buildPythonPackage
 , fetchPypi
+, isPy3k
+, lib
 }:
 
 buildPythonPackage rec {
   pname = "argon2_cffi";
   version = "19.1.0";
-  name    = "${pname}-${version}";
 
   src = fetchPypi {
     inherit pname version;
     sha256 = "81548a27b919861040cb928a350733f4f9455dd67c7d1ba92eb5960a1d7f8b26";
   };
 
-  propagatedBuildInputs = [ cffi six ];
+  propagatedBuildInputs = [ cffi six ] ++ lib.optional (!isPy3k) enum34;
   checkInputs = [ hypothesis pytest wheel ];
   checkPhase = ''
     pytest tests
   '';
 
-  meta = {
+  meta = with lib; {
     description = "Secure Password Hashes for Python";
     homepage    = https://argon2-cffi.readthedocs.io/;
+    license     = licenses.mit;
   };
 }