asymetric arrays lead to a crash. the asymetry was introduce
in the previous commit. This change fixes the crash and I think
it will keep the single cell case fixed too.

fdd23770 numpy_interface: handle mpi4py not being available
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Utkarsh Ayachit <utkarsh.ayachit@kitware.com>
Merge-request: !4723

Give a better error message for a missng mpi4py. In addition, only try
if there is more than one processor actually in use.

b304e92d TextExtraction: modernize layout of threshold array
39ef92b6 TestExtraction: Change test data arrays to vtkFloatArray
e70bd603 Handle selection of non-vtkDoubleArrays
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Utkarsh Ayachit <utkarsh.ayachit@kitware.com>
Merge-request: !4711

Making this modification ensures that threshold selections work for
not just vtkDoubleArrays.

Threshold selection was not working for non-double arrays because the
fast data array dispatch assumes the data array and threshold array
are the same type. However, the threshold array type is always double,
so threshold selection would not work for any other array type.

Fixed by adding a slow-API data array access path to handle threshold
selection of non-double data arrays.

b75faf9d Merge branch 'upstream-diy2' into fix-diy-installation
713a26f4 diy2 2018-09-24 (3298ccb3)
c7e6181e diy2: update the snapshot to use
248cf8a3 diy2: fix mangling
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4702

* upstream-diy2:
  diy2 2018-09-24 (3298ccb3)

Code extracted from:

    https://gitlab.kitware.com/third-party/diy2.git

at commit 3298ccb3fd5af6d85fef9f0416f04f7587ddffc1 (for/vtk-20180924-g3298ccb3).

The install directory wasn't working properly.

f05117cd vtkPResampleWithDataSet: update for new diy API changes
cad967ee Merge branch 'upstream-diy2' into update-diy-20180918
5789e33e diy2 2018-09-18 (f402e419)
ad9f7b29 diy2: update the reference tag
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Sujin Philip <sujin.philip@kitware.com>
Merge-request: !4682

88120022 fix RubberBandZoom front buffer usage
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Utkarsh Ayachit <utkarsh.ayachit@kitware.com>
Acked-by: Cory Quammen <cory.quammen@kitware.com>
Merge-request: !4677

* upstream-diy2:
  diy2 2018-09-18 (f402e419)

Code extracted from:

    https://gitlab.kitware.com/third-party/diy2.git

at commit f402e4190bf285698d9b5e2f8f7bf49d3c96d83b (for/vtk-20180918-g8359566d).

4d5c903c Fix point picking used with cell scalars
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Utkarsh Ayachit <utkarsh.ayachit@kitware.com>
Merge-request: !4655

The old code would incorrectly index into a cell indexed
texture buffer when using points.

871ae8f3 Add all parameters for Principled material of OSPRay
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: David E. DeMarle <dave.demarle@kitware.com>
Acked-by: Mathieu Westphal <mathieu.westphal@kitware.com>
Merge-request: !4640

ca8299a3 doc: Improve QVTKOpenGLWidget docstring
ee8d79a1 Rename QVTKOpenGLSimpleWidget to QVTKOpenGLNativeWidget
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Cory Quammen <cory.quammen@kitware.com>
Merge-request: !4642

bcfaf23a rev VTKExamples to 8c4ceec93b11b9b64db4e57ee2d644d95f8f8115
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4629

b19ebfe6 General code cleanup for the Tecplot reader
08f8e562 Updated vtkTecplotReader to handle ZONETYPE
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4637

Some transparency changes and other changes see VTKExmaples

48861127 Avoid unnecessary allocation of vtkInformation
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: David Thompson <david.thompson@kitware.com>
Merge-request: !4639

d8aa5b89 Misc. typo fixes
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !4638

d5d3cc2a Add documentation for Lagrange tetra, triangle
26c258c2 Fix Lagrange wedge shape fns and derivatives
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: David Thompson <david.thompson@kitware.com>
Merge-request: !4632

Calling Modified on any vtkDataArray caused an vtkInformation instance
to be created if none existed yet. This leads to unnecessary dynamic
memory allocation and deallocation.

Solved by testing whether the array has a vtkInformation instance before
getting it and resetting its keys.

505c20a2 Adding a cmake_minimum_required on FindOpenMP.cmake
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Robert Maynard <robert.maynard@kitware.com>
Merge-request: !4634

Found via `codespell`

f9b02b1a Add support for 2 new elements to Exodus files.
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: T.J. Corona <tj.corona@kitware.com>
Merge-request: !4636

The 15-node tetrahedron and 21-node wedge are now supported
in VTK via the vtkLagrangeTetra and vtkLagrangeWedge.