Fix the way _argparse.py is imported as a backup (Python 2.6 systems)
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
Several python modules attempt to import argparse and if this fails (Python 2.6), then attempt to locally import _argparse.py from our repo. However, we had several copies of _argparse.py and not even in all the places they were needed, so many of those backup imports would have failed if they were even encountered.
We need just a single place in all of vtk/paraview where we can count on _argparse.py being located, and then every module that needs it as a backup can import it from there.
The one exception is when it is needed as a part of the build process, and we should leave it available locally in the single directory where it is needed.