anchor.diff:  }:
   
   let
  -  version = "16.5.0";
  +  version = "16.6.0";
   in
   buildPythonPackage rec {
     name = "Twisted-${version}";
  
positive.code: , buildPythonPackage
  , fetchPyPi
  , isPy3k
  
  , constantly
  , incremental
  
negative.code:   # Tests are not fully compatible with Python 3
    doCheck = !isPy3k;
  
    meta = with lib; {
      description = "An event-driven networking engine written in Python";
      homepage = https://twistedmatrix.com/;
      license = licenses.mit;
  