`py-h5py` wraps the HDF5 library. It contains these lines: ``` Python depends_on('hdf5@1.8.4:+mpi', when='+mpi') depends_on('hdf5@1.8.4:~mpi', when='~mpi') depends_on('mpi', when='+mpi') ``` The first two of these should probably read instead ``` Python depends_on('hdf5@1.8.4:') depends_on('hdf5+mpi', when='+mpi') ``` This would allow using a plain `h5py` (which is `h5py~mpi`) with a `hdf5+mpi`. I don't think there is a reason to disallow this.