anchor.diff: -{ stdenv, buildPythonPackage, fetchPypi, isPy3k, pythonOlder
  +{ stdenv, lib, buildPythonPackage, fetchPypi, isPy3k, pythonOlder
   , attrs, click, cligj, click-plugins, six, munch, enum34
  -, pytest, boto3, mock
  +, pytest, boto3, mock, giflib
   , gdal_2 # can't bump to 3 yet, https://github.com/Toblerity/Fiona/issues/745
   }:
   
  
positive.code:     sha256 = "0gpvdrayam4qvpqvz0911nlyvf7ib3slsyml52qx172vhpldycgs";
    };
  
    CXXFLAGS = stdenv.lib.optionalString stdenv.cc.isClang "-std=c++11";
  
    nativeBuildInputs = [
      gdal_2 # for gdal-config
  
negative.code: 
    buildInputs = [
      gdal_2
    ] ++ lib.optionals stdenv.cc.isClang [ giflib ];
  
    propagatedBuildInputs = [
      attrs
  