Add error message when failing to load DAQModule plugins

[eflumerf]

Description

Add an ers::error report of DAQModuleCreationFailed to ensure output when running in unit tests.

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature or enhancement (non-breaking change which adds functionality)
• Optimization (non-breaking change that improves code/performance)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

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))

[eflumerf]

Possibly something in DUNE-DAQ/logging#45

[bieryAtFnal]

I confirm that I see the following message in the output from the appfwk unit tests when I use the code on this branch.

2026-Jun-30 10:57:36,136 ERROR [dunedaq::appfwk::make_module(...) at /home/nfs/biery/dunedaq/30JunFDDevLBIteratorTesting/sourcecode/appfwk/include/appfwk/detail/DAQModule.hxx:48] Failed to create DAQModule error_test of type not_a_real_plugin_name
  IllegalUnderscore. Library specification "not_a_real_plugin_name" contains an illegal underscore.

[eflumerf]

I confirm that I see the following message in the output from the appfwk unit tests when I use the code on this branch.

2026-Jun-30 10:57:36,136 ERROR [dunedaq::appfwk::make_module(...) at /home/nfs/biery/dunedaq/30JunFDDevLBIteratorTesting/sourcecode/appfwk/include/appfwk/detail/DAQModule.hxx:48] Failed to create DAQModule error_test of type not_a_real_plugin_name
  IllegalUnderscore. Library specification "not_a_real_plugin_name" contains an illegal underscore.

Wait, this is really interesting! Apparently, the unit test has been testing the wrong thing all this time! The intent was to test trying to load a plugin type that doesn't exist, but apparently we've actually been testing an invalid plugin name format!

[bieryAtFnal]

I confirm that I now see two "new" error messages:

2026-Jun-30 11:36:55,152 ERROR [dunedaq::appfwk::make_module(...) at /home/nfs/biery/dunedaq/30JunFDDevLBIteratorTesting/sourcecode/appfwk/include/appfwk/detail/DAQModule.hxx:48] Failed to create DAQModule error_test of type not_a_valid_plugin_name
	was caused by: 2026-Jun-30 11:36:55,152 ERROR [ers::Issue::Issue(...) at /tmp/root/spack-stage/spack-stage-ers-NB_DEV_260630_A9-75xklo2djghuvo5ygosqin2djbaadupl/spack-src/src/Issue.cpp:102] ---- LogicError BEGIN
  IllegalUnderscore. Library specification "not_a_valid_plugin_name" contains an illegal underscore.
  The class name and path to it may not contain an underscore. If this is a configuration error, plase correct it; if the module's class name or its location within its enclosing package really do have an underscore this situation must be rectified.
---- LogicError END

and

2026-Jun-30 11:38:54,476 ERROR [dunedaq::appfwk::make_module(...) at /home/nfs/biery/dunedaq/30JunFDDevLBIteratorTesting/sourcecode/appfwk/include/appfwk/detail/DAQModule.hxx:48] Failed to create DAQModule error_test of type not-a-real-plugin-name
	was caused by: 2026-Jun-30 11:38:54,476 ERROR [ers::Issue::Issue(...) at /tmp/root/spack-stage/spack-stage-ers-NB_DEV_260630_A9-75xklo2djghuvo5ygosqin2djbaadupl/spack-src/src/Issue.cpp:102] ---- Configuration BEGIN
  UnknownPlugin
  ---- Configuration BEGIN
    Library specification "not-a-real-plugin-name" does not correspond to any library in CET_PLUGIN_PATH of type "duneDAQModule"
  ---- Configuration END
  Plugin not-a-real-plugin-name with version Unknown was not registered.
  Perhaps your plugin type is misspelled or is not a plugin recognized by this
  system.
---- Configuration END