Bug#944769: python3-h5py fails to import if offline due to apparent MPI failure

[Drew Parsons]

Source: h5py
Followup-For: Bug #944769

Thanks for your analysis, Thibaut.  Testing OMPI_COMM_WORLD_SIZE and
MPI_LOCALNRANKS is a decent idea.  Fair enough that non-MPI users
shouldn't have to worry about MPI settings (the MPI capability should
be transparent if not explicitly invoked).

Drew