anchor.diff:      # Needed to run the tests reliably. See:
       # https://bitbucket.org/mpi4py/mpi4py/issues/87/multiple-test-errors-with-openmpi-30
       export OMPI_MCA_rmaps_base_oversubscribe=yes
  -    export OMPI_MCA_osc=sm
  -    export OMPI_MCA_btl=self,vader
     '';
   
     setupPyBuildFlags = ["--mpicc=${mpi}/bin/mpicc"];
  
positive.code:   passthru = {
      inherit mpi;
    };
  
    postPatch = ''
      substituteInPlace test/test_spawn.py --replace \
  
negative.code: { stdenv, fetchPypi, fetchpatch, python, buildPythonPackage, mpi, openssh }:
  
  buildPythonPackage rec {
    pname = "mpi4py";
  