anchor.diff:  
     buildInputs = [ cmake boost ];
   
  -  propagatedBuildInputs = with pythonPackages; [ waitress frozendict bottle ];
  +  propagatedBuildInputs = [ waitress frozendict bottle ];
   
     buildPhase = ''
       export EXTRA_CMAKE_ARGS=-DPATH_TO_LLVM_ROOT=${llvmPackages.clang-unwrapped}
  
positive.code: { stdenv, fetchgit, cmake, python, llvmPackages, boost, pythonPackages
  }:
  
  let
    inherit (pythonPackages) python;
  in pythonPackages.mkPythonDerivation rec {
    name = "ycmd-2016-01-12";
    namePrefix = "";
  
  
negative.code: 
    configurePhase = ":";
  
    installPhase = ''
      mkdir -p $out/lib/ycmd/third_party $out/bin
      cp -r ycmd/ CORE_VERSION libclang.so.* ycm_client_support.so ycm_core.so $out/lib/ycmd/
      ln -s $out/lib/ycmd/ycmd/__main__.py $out/bin/ycmd
  