Use pytest.fail and short status messages to indicate failures.

[eflumerf]

Description

See title.

Type of change

• New feature or enhancement (non-breaking change which adds functionality)

Testing checklist

• Unit tests pass (e.g. dbt-build --unittest)
• Minimal system quicktest passes (pytest -s minimal_system_quick_test.py)
• Full set of integration tests pass (dunedaq_integtest_bundle.sh)
• Python tests pass if applicable (e.g. python -m pytest)
• Pre-commit hooks run successfully if applicable (e.g. pre-commit run --all-files)

Comments here on the testing

Further checks

• Code is commented where needed, particularly in hard-to-understand areas
• Code style is correct (dbt-build --lint, and/or see https://dune-daq-sw.readthedocs.io/en/latest/packages/styleguide/)
• If applicable, new tests have been added or an issue has been opened to tackle that in the future.
  (Indicate issue here: # (issue))

[bieryAtFnal]

These changes look good to me. It will be good to use this model in other regression tests and probably in the integrationtest infrastructure, but I'm reluctant to commit to doing that for fddaq-v5.7.0. But, we should make a note for the next release.

For reference, here is what I see at the end of the MSQT when I bugger the expected fragment sizes and include these changes:

=================================== FAILURES ===================================
_________ test_data_files[MinimalSystem-StandAloneSSH_PM-run_dunerc0] __________
Trigger_Candidate Fragment size check failed. WIBEth Fragment size check failed. 
=========================== short test summary info ============================
FAILED minimal_system_quick_test.py::test_data_files[MinimalSystem-StandAloneSSH_PM-run_dunerc0]
========================= 1 failed, 3 passed in 55.40s =========================

and here is what we saw before these changes:

=================================== FAILURES ===================================
_________ test_data_files[MinimalSystem-StandAloneSSH_PM-run_dunerc0] __________
minimal_system_quick_test.py:156: in test_data_files
    assert all_ok
E   assert False
=========================== short test summary info ============================
FAILED minimal_system_quick_test.py::test_data_files[MinimalSystem-StandAloneSSH_PM-run_dunerc0]
========================= 1 failed, 3 passed in 53.49s =========================