Misc fixes for python 3.
  -- Python 3 now works locally if using patched SWIG.
  -- Anyone who wants to should wait for swig 3.0.3 or patch swig 3.0.2 with
     https://github.com/swig/swig/pull/207
  -- Remember to generate your swig interface using python3 executable

       python3 cmake/scripts/generate-swig-interface