anchor.diff:  { lib
   , buildPythonPackage
   , isPy27
  -, pathlib
   , fetchPypi
  +, imageio-ffmpeg
  +, numpy
   , pillow
   , psutil
  -, imageio-ffmpeg
  -, pytest
  -, numpy
  -, isPy3k
  -, ffmpeg_3
  -, futures ? null
  -, enum34
  +, pytestCheckHook
   }:
   
   buildPythonPackage rec {
  
positive.code:     inherit pname version;
    };
  
    checkInputs = [ pytest psutil ] ++ lib.optionals isPy3k [
      imageio-ffmpeg ffmpeg_3
      ];
    propagatedBuildInputs = [ numpy pillow ];
  
    checkPhase = ''
      export IMAGEIO_USERDIR="$TMP"
      export IMAGEIO_NO_INTERNET="true"
      export HOME="$(mktemp -d)"
      py.test
    '';
  
    # For some reason, importing imageio also imports xml on Nix, see
    # https://github.com/imageio/imageio/issues/395
  
    # Also, there are tests that test the downloading of ffmpeg if it's not installed.
    # "Uncomment" those by renaming.
    postPatch = ''
      substituteInPlace tests/test_meta.py --replace '"urllib",' "\"urllib\",\"xml\","
      substituteInPlace tests/test_ffmpeg.py --replace 'test_get_exe_installed' 'get_exe_installed'
    '';
  
    meta = with lib; {
  
negative.code:     homepage = "http://imageio.github.io/";
      license = licenses.bsd2;
    };
  }
  