Bug#910247: python3-netgen: importing netgen.gui fails due to MPI_Comm_size()

[Drew Parsons]

Package: python3-netgen
Version: 6.2.2006+really6.2.1905+dfsg-10
Followup-For: Bug #910247

As a workaround, initialise MPI before importing netgen.gui.

> from mpi4py import MPI
> import netgen.gui