Tests for publishers

I am trying to build up a very basic testing framework so we can tests
our publishers. The idea is to provide a YAML input file and expected
XML output, run the parser on the YAML file and compares its output with
the fixture XML.

That test suite should speed up development of new publishers.

TestCaseModulePublisher is declared inside a function so that unittest
discovery does not consider it a usable test directly. load_test is
responsible for instantiating the test suite.

Change-Id: If3260113eb1337ac47c3883b11c600e5a595dae3
[fabre.arnaud@gmail.com: fixed some runtime errors]
Signed-off-by: Arnaud Fabre <fabre.arnaud@gmail.com>
Merge "Tests for publishers"