anchor.diff:  
     pyodbc = buildPythonPackage rec {
       name = "pyodbc-3.0.7";
  +    disabled = isPyPy;  # use pypypdbc instead
   
       src = fetchurl {
         url = "https://pyodbc.googlecode.com/files/${name}.zip";
  
positive.code:     };
    };
  
    ipdb = buildPythonPackage {
      name = "ipdb-0.7";
      src = fetchurl {
        url = "http://pypi.python.org/packages/source/i/ipdb/ipdb-0.7.tar.gz";
        md5 = "d879f9b2b0f26e0e999809585dcaec61";
      };
      propagatedBuildInputs = [ pythonPackages.ipythonLight ];
    };
  
negative.code: 
    zfec = buildPythonPackage (rec {
      name = "zfec-1.4.24";
      disabled = isPyPy;
  
      src = fetchurl {
        url = "http://pypi.python.org/packages/source/z/zfec/${name}.tar.gz";
  