Message12994

When we compile, since #2044, we make class files private to the current user.

When we install, the files come out of a JAR. Since the process does not preserve permissions, the files have the default permissions for the installing user, 
and end up world-readable (fortuitously, almost). 

However, we also run an installation script for pip, and at that point it seems we recompile a proportion (not all) of the library. These class files become private to the installing user. I believe this happens because either :

1. the source appears newer because we touch it somehow after the class is created.
2. the source time in the class file does not match the one rounded by the JAR format. 

This is a Bad Thing generally, and not just because it has this effect. It will makes Jython try to ignore (always try to rewrite) compiled version we supply. Good discovery.

At the moment, I'm looking at the rounding theory.