anchor.diff:        license = "BSD-style";
       };
     });
  -  
  +
     dask = buildPythonPackage rec {
       name = "dask-${version}";
       version = "0.7.0";
  -    
  +
       src = pkgs.fetchurl {
         url = "https://pypi.python.org/packages/source/d/dask/${name}.tar.gz";
         sha256 = "3b48646e9e66ec21a6885700d39ea90e2c2a7ad5d26773a8413b570eb1a67b3e";
       };
  -    
  +
       propagatedBuildInputs = with self; [numpy toolz dill];
  -    
  +
       meta = {
         description = "Minimal task scheduling abstraction";
         homepage = "http://github.com/ContinuumIO/dask/";
  
positive.code:       maintainers = with maintainers; [ phreedom thoughtpolice ];
      };
    });
    
    objgraph = buildPythonPackage rec {
      name = "objgraph-${version}";
      version = "2.0.1";
      
      src = pkgs.fetchurl {
        url = "https://pypi.python.org/packages/source/o/objgraph/${name}.tar.gz";
        sha256 = "841de52715774ec1d0e97d9b4462d6e3e10406155f9b61f54ba7db984c45442a";
      };
      
      # Tests fail with PyPy.
      disabled = isPyPy;
      
      propagatedBuildInputs = with self; [pkgs.graphviz];
      
      meta = {
        description = "Draws Python object reference graphs with graphviz";
        homepage = http://mg.pov.lt/objgraph/;
  
negative.code:       license = licenses.mit;
      };
    });
  
    xray = buildPythonPackage rec {
      name = "xray-${version}";
      version = "0.6.0";
  
      src = pkgs.fetchurl {
        url = "https://pypi.python.org/packages/source/x/xray/${name}.tar.gz";
        sha256 = "c8c4aadb0d39662a81c259bd609f42708ff31c90012a9dd0a1f9ee56a798196f";
      };
  
      buildInputs = with self; [nose];
      propagatedBuildInputs = with self; [numpy pandas];
  
      meta = {
        description = "N-D labeled arrays and datasets in Python";
        homepage = https://github.com/xray/xray;
        license = licenses.asl20;
      };
    };
  
    youtube-dl = callPackage ../tools/misc/youtube-dl {
  