use testCase.assert instead of assert and try...except

In unit tests, we should use: self.assertTrue or self.assertFalse
instead of 'assert xxx is True/False', and use self.assertRaises instead
of 'try ... except ...'

fixes bug #1212602

Change-Id: I25318eb59cd26a98afdce5495273e3b3266655a4
Merge "use testCase.assert instead of assert and try...except"