If you used older version of the py distribution (which included the py.test command line tool and Python name space) you accessed helpers and possibly collection classes through the py.test Python namespaces. The new pytest Python module flaty provides the same objects, following these renaming rules:
py.test.XYZ -> pytest.XYZ
py.test.collect.XYZ -> pytest.XYZ
py.test.cmdline.main -> pytest.main
The old py.test.* ways to access functionality remain valid but you are encouraged to do global renaming according to the above rules in your test code.