functional.common.tests module defines:
* assertOutput (similar to assertEqual)
* assertInOutput (similar to assertIn)
in order to allow the usage of assertions in testcase classmethods but
there is no reason to use them in testcase instancemethods at least
because they raise Exception instances instead of AssertionError
instances.
Change-Id: I9ffcaf9c6e6a1ff5df6ea2d79be3fb4496db4b85