Instead of returning an empty dataset, raise an exception when filtering on the tag that does not exist.
e.g. one will get:
$ apd-list-pfns SL rds_hadronic --tag event_type --value 13863401 --polarity magdown ValueError: Tag event_type unknown. Did you mean eventtype ? Available tags: config, polarity, eventtype, datatype, version, name, state
To be merged after !24 (merged) as it includes it too to have the changes on the gitlab-ci.
Closes #10 (closed)