no mpi4py + mpirun for plotting

[mathematicalmichael]

this peculiar corner case happens to lead to failure of the plotDomains tests.
super low priority to fix, but pip install . does not handle mpi4py right now, and the test should skip but doesn't because technically it detects one processor.

To solve, I think we can use the __init__.py files to flag down whether we are faking MPI or not, and use that as the skip condition instead of processor count.

[smattis]

For which version of python is pip install mpi4py not working now? Was the the hosting server possibly just down?

[mathematicalmichael]

I never said it wasnt working. Just that in the event that it was forgotten to be installed (it’s not part of our requirements, technically, it has to be manually added), plotting tests detect one processor and fail to pass.

Our travis CI only tests in serial after mpi4py is uninstalled at the end. I’m saying that if we added an mpirun test as the final line there, it wouldn’t work, not for any functional reason, just a weird quirk.