Message9256

So posix is not missing, that's the important one. You can alternatively try to use the subprocess module, and see if that works at all. There's also a small chance that this bug, recently fixed, might be causing the underlying problem:
http://bugs.jython.org/issue2205, but you are not reporting these exceptions being thrown.

As for the remaining differences, _imp, _json, _jythonlib are newly added since beta 3:
* _imp used to be called imp, but in the process of adding some functionality to the imp module (NullImporter), I chose to write it in Python and place it in Lib/imp.py rather than in Java, since that's way easier. My preference is always to reserve writing Java for code that is either performance intensive or can cause other issues, such as seen in our object proxying support.
* _json is for the port of json.c
* _jythonlib is a new module for managing some newly exposed Jython runtime internals - in part to minimize having said object proxying code in Java, using _jythonlib's new support