Some tests used incorrect order assertIs(observed, expected).
The correct order expected by testtools is
assertIs(expected, observed, message='')
Assert that expected is observed.
Parameters:
expected The expected value.
observed The observed value.
message An optional message describing the error.
https://docs.python.org/2/library/unittest.html
Change-Id: I5f406336b7804c13ca042dd0c6b30645a711c5f2