Adding a breakpoint() before the assert on L104, and continuing until source is empty:
(Pdb) where
/omd/sites/monitoring/bin/cmk(79)<module>()
-> errors = config.load_all_agent_based_plugins(check_api.get_check_api_context)
/omd/sites/monitoring/lib/python3/cmk/base/config.py(1415)load_all_agent_based_plugins()
-> errors.extend(load_checks(get_check_api_context, filelist))
/omd/sites/monitoring/lib/python3/cmk/base/config.py(1563)load_checks()
-> errors = (_extract_agent_and_snmp_sections(validate_creation_kwargs=did_compile) +
/omd/sites/monitoring/lib/python3/cmk/base/config.py(1986)_extract_agent_and_snmp_sections()
-> create_snmp_section_plugin_from_legacy(
/omd/sites/monitoring/lib/python3/cmk/base/api/agent_based/register/section_plugins_legacy/__init__.py(235)create_snmp_section_plugin_from_legacy()
-> detect_spec = create_detect_spec(
/omd/sites/monitoring/lib/python3/cmk/base/api/agent_based/register/section_plugins_legacy/convert_scan_functions.py(398)create_detect_spec()
-> _compute_detect_spec(
/omd/sites/monitoring/lib/python3/cmk/base/api/agent_based/register/section_plugins_legacy/convert_scan_functions.py(366)_compute_detect_spec()
-> scan_func_ast = _get_scan_function_ast(section_name, scan_function, fallback_files)
> /omd/sites/monitoring/lib/python3/cmk/base/api/agent_based/register/section_plugins_legacy/convert_scan_functions.py(105)_get_scan_function_ast()
-> assert source != "", "Files: %r" % ((read_files, src_file_name),)
(Pdb) dir()
['fallback_files', 'name', 'read_files', 'snmp_scan_function', 'source', 'src_file_name']
(Pdb) print(source)
(Pdb) print(name)
fast_lta_volumes
(Pdb) print(src_file_name)
None
(Pdb) print(fallback_files)
[]
So for some reason the source filename is empty. Investigating further.