python 2 is EOL and no python 3 support

[jdshpe]

The python in this project has not been updated to support python 3 when python 2 was declared EOL on January 1st 2020.

[lee218llnl]

@jdshpe this is a pretty big task. Pynamic is based on pyMPI and pyMPI has not been supported for many years now and was never ported to Python 3. Ultimately we would need a way to port Pynamic to mpi4py, but then we lose the ability to produce a pynamic-pyMPI executable with the shared objects linked in to the executable. We may have to only support pure dynamic loading. I'm not sure when I will get around to doing this.