PY3: New test for the get_params handling of deprecated attributes.

This test passes under Python 2.7 but currently fails under Python
3.2+. This change of behavior makes many doctest fail under Python 3
while they pass under Python 2.

The goal of this test is to help find the cause of the issue under
Python 3 and also act as a non regression test once a fix is found
under Python 3.