python: refcounting for the handle's PyObjects.

Returned values from PyCFunctions need to have the refcount increased [1],
else segfaults (or worse) emerge.

The unit test doesn't look like it does much, but in fact it pretty
reliably reproduces a segfault.

[1] http://docs.python.org/2/c-api/structures.html?highlight=pycfunction#PyCFunction