Cookies with the "SameSite" flag set to None and without the "secure"
flag will be soon rejected by latest browser versions.
This affects sessions and messages cookies.
Backport of 240cbb63bf 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.
Mariusz Felisiak
Jon Dufresne
Osaetin Daniel
Nick Pope
Bernhard M. Wiedemann
Alex Gaynor
Alvin Lindstam
Tim Graham