BUG: Use absolute module path PyCapsule_Import

[thewtex]

Addresses:

ImportError: PyCapsule_Import could not import module "_ITKCommonPython"

That can occur when unpickling for Dask, for example.

According to the PyCapsule_Import documentation, internally it calls
PyImport_ImportModule. According to the PyImport_ImportModule
documentation, this requires the absolute path -- we add the itk.
prefix.

In most other contexts, the _ITKCommonPython module is likely to
already be imported. Since _ITKCommonPython gets loaded via
PyImport_ImportModule, it is not registered with the ITK lazy loading
module system, so we add from . import _ITKCommon.

[GenevieveBuckley]

This looks good to me. Thanks for working on it!

I can't say for sure it will for sure fix the dask example (I wasn't able to build ITK last time I tried, so I can't test it now), but I certainly can't see this causing any problems for either ITK or dask.

[PranjalSahu]

import dask
import itk
from dask import delayed

if __name__== "__main__":
    from dask.distributed import Client, LocalCluster
    cluster = LocalCluster()
    client = Client(cluster)

    @delayed
    def performsum(m):
        return m.GetNumberOfPoints()

    m = itk.Mesh[itk.F, 3].New()
    a = performsum(m).compute()
    print(a)

Tested with a locally built wheel.
It works fine.