The module backports features to Python 2.6 and 2.7. If it is available,
the tests will use it. If it is not available, it will fall back to
regular unittest. On Python 2.7, the tests pass anyway. On Python 2.6,
there are failures with Python 2.6.
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>