Skip tests with external artifacts
The following tests need (large) files not included in the repository:
FAILED tests/archive/test_archive.py::test_read_springer - AttributeError: 'NoneType' object has no attribute 'seek'
FAILED tests/normalizing/test_material.py::test_material_bulk - assert None
FAILED tests/normalizing/test_system.py::test_springer_normalizer - IndexError: list index out of range
These tests should be skipped if the data is not available. Additionally, we could explain how to get this data, or provide a script.