Prior to introducing the pytest runner, clean.sh files were used as a
list of files that the test is expected to leave around as artifacts and
check that no extra files were created.
With the pytest runner, those scripts are no longer used, but the
ability to detect extraneous files is still useful. Add a new
"extra_artifacts" mark which can be used for the same purpose.
Instead of invoking get_algorithms.py script repeatedly (which may yield
different results), move the algorithm configuration to an isctest
module. This ensures the variables are consistent across the entire test
run.
Ensure pytest picks up our python test modules, since we're using
tests_*.py convention, which is different from the default.
Configure pytest logging to display the output from all tests (even the
ones that passed). This ensures we have sufficient amount of information
to debug test post-mortem just from the artifacts.
