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Backport of 240cbb63bf9965c63d7a3cc9032f91410f414d46 from master
* assertIsNone()/assertIsNotNone() instead of comparing to None.
* assertLess() for < comparisons.
* assertIs() for 'is' expressions.
* assertIsInstance() for isinstance() expressions.
* rounding of assertAlmostEqual() for round() expressions.
* assertIs(..., True/False) instead of comparing to True/False.
* assertIs()/assertIsNot() for ==/!= comparisons.
* assertNotEqual() for == comparisons.
* assertTrue()/assertFalse() instead of comparing to True/False.
