anchor.diff:  { stdenv, fetchPypi, isPy27, python, buildPythonPackage
   , numpy, hdf5, cython, six, pkgconfig, unittest2, fetchpatch
  -, mpi4py ? null, openssh }:
  +, mpi4py ? null, openssh, pytest }:
   
   assert hdf5.mpiSupport -> mpi4py != null && hdf5.mpi == mpi4py.mpi;
   
  
positive.code: 
    preBuild = if mpiSupport then "export CC=${mpi}/bin/mpicc" else "";
  
    checkInputs = optional isPy27 unittest2 ++ [ openssh ];
    nativeBuildInputs = [ pkgconfig ];
    buildInputs = [ hdf5 cython ]
      ++ optional mpiSupport mpi;
  
negative.code:   mpi = hdf5.mpi;
    mpiSupport = hdf5.mpiSupport;
  in buildPythonPackage rec {
    version = "2.10.0";
    pname = "h5py";
    disabled = isPy27;
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "84412798925dc870ffd7107f045d7659e60f5d46d1c70c700375248bf6bf512d";
    };
  
    configure_flags = "--hdf5=${hdf5}" + optionalString mpiSupport " --mpi";
  
  