Minor test failures in v4.0.1 install

Minor test failures from installation of CDDS v4.0.1;
```
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_extract/test_validate.py::TestValidate::test_calculate_file_frequency - AttributeError: The "variable_list_file" does not exist.
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_extract/test_validate.py::TestValidate::test_configure_mapping_for_each_variable - AttributeError: The "variable_list_file" does not exist.
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_extract/test_validate.py::TestValidate::test_process_pp_streamtype - AttributeError: The "variable_list_file" does not exist.
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_validate/test_request_validations.py::TestValidations::test_cmip6_parent_validations - AssertionError: False is not true
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_validate/test_request_validations.py::TestValidations::test_cmip6_validations - AssertionError: False is not true
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_validate/test_request_validations.py::TestValidations::test_cordex_validations - AssertionError: False is not true
FAILED ../conda_environments/cdds-4.0.1/lib/python3.12/site-packages/cdds/tests/test_validate/test_request_validations.py::TestValidations::test_invalid_stream_validations - AssertionError: Lists differ: ['The "variable_list_file" does not exist.'] != ['Stream unknown is not in the model parame[35 chars]sed']
```

I'm happy that this is just an issue with the test construction, not an issue with the code itself.

Suspect that this is down to issues with code change introduced in #1042