Bug#1141884: libvtk9.x ships python library without proper shlibs

[Drew Parsons]

Package: vtk9
Followup-For: Bug #1141884

Building vtk9 for all supported python is a grand challenge
because of the cmake problem:  cmake does not easily build support for
multiple python version. It can manage selection of version, but not
multiple in the same build.

Building for non-default python could possibly be set up, but it's a
bit of effort, and I'm not sure it wouldn't give auxiliary problems,
e.g. VTK C++ modules (not python modules) linking to a specific
libpython3.Y.so, which can't be managed so easily.
e.g. Rendering/PythonContext2D,
/usr/lib/x86_64-linux-gnu/libvtkPythonContext2D-9.6.so links to
libvtkWrappingPythonCore3.14-9.6.so.1 

Your second idea might be the only practical way to manage it,
set up a dummy dependency so vtk9 catches the python default
transitions.