Many places in tests code use assertEqual(AA, None),
the same with True and False and negatives of such comparisons.
As comparison to singletons must use `is` operator, appropriate usage
is assertIs, assertIsNot, assertIsNone, assertIsNotNone
These assertions are provided by the `testtools` package,
so this change is not breaking backward compatibility with Python 2.6
Change-Id: I232136ce49afdb8bf78b42221454540471d12c23
Closes-Bug: #1259023