What is the benefit of running the system wide cython? I do see that some other cython-based packages do choose to run cython (or at least build-depend on cython). Unfortunately the current lack of a python3-cython package would prevent us from running cython on the python3-mpi4py build anyway. :(
bin/python-mpi: Yes, it's a new "feature" but it is of questionable relevance. I have yet to encounter an actual use case, as the "from mpi4py import MPI" line in your code runs the same MPI_Init routine. Perhaps this might be of use with certain versions of MPI? Regardless, the setup.py script installs this file into /.../dist-packages/mpi4py/bin/python-mpi which is outside the default PATH. I suppose we should move this to /usr/bin/pythonX.Y-mpi? The lib-pmpi/*.so files do seem to be used by some profiling feature. I've re-included them and updated the package.
