When parallel, install exception hook to MPI.Abort

Otherwise, if a single rank raises an exception and participates in
an outstanding barrier, this barrier is never reached by all ranks
and the program hangs indefinitely.

If running in parallel, install an exception hook that is invoked
whenever an exception is not caught and causes an MPI Abort after
the regular exception hook has fired printing a backtrace etc.

see: https://groups.google.com/d/msg/mpi4py/RovYzJ8qkbc/n_Wqjnha2F0J