anchor.diff:    };
   
     nativeBuildInputs = [ pkgconfig ];
  -  buildInputs = [ pythonPkg libftdi1 ];
  +  buildInputs = [ passthru.pythonPkg libftdi1 ];
     makeFlags = [ "PREFIX=$(out)" ];
   
     enableParallelBuilding = true;
  
positive.code:   pname = "icestorm";
    version = "2019.09.13";
  
    pythonPkg = if usePyPy then pypy3 else python3;
    pythonInterp = pythonPkg.interpreter;
  
    src = fetchFromGitHub {
      owner  = "cliffordwolf";
  
negative.code:       --replace /usr/local/share "$out/share"
  
      for x in icefuzz/Makefile icebox/Makefile icetime/Makefile; do
        substituteInPlace "$x" --replace python3 "${passthru.pythonInterp}"
      done
  
      for x in $(find . -type f -iname '*.py'); do
        substituteInPlace "$x" \
          --replace '/usr/bin/env python3' '${passthru.pythonInterp}'
      done
    '';
  
  