Hi Tom:

Ahh I thought that was part of the original Zope code. Thanks for correcting me.

Yes, there are a few different python implementations. 
CPython is what most of us use. PyPy and MicroPython are two native
implementations, then there is jython (python written in java)
and a couple of others.

PyPy uses just in time compilation to speed things up. Guido (the former Python BDFL)
is looking at that for speeding up CPython.

PyPy provides the whole python standard library. It looks like symtable.py imports 
_symtable. IIUC _symtable is written in C in the CPython core/binary/interpreter.
So PyPy needs to implement their own version.

I may try the python2 code under PyPy to see if it works. If so I can special
case the code based on whether symtable imports correctly. However I suspect the
python2 version won't work but who knows.

Thanks for the additional info.