Energy ratio adjustments

[megies]

What does this PR do?

Minor adjustments in new energy ratio triggers, raise ValueError on nonsensical input values instead of returning zero-filled arrays.

CC @dizcza

Why was it initiated? Any relevant Issues?

minor adjustement to #3161
see #3161 (review)

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[dizcza]

LGTM, save for I'd use assertRaises without any expected message as (1) the message could change in the future and (2) you duplicate code by doing that.

Also, consider switching to either pytest or unittest. You have a mix of both and I don't see a reason for that.

[d-chambers]

Also, consider switching to either pytest or unittest. You have a mix of both and I don't see a reason for that.

The reason the mix exists is because we are transitioning from unittest to pytest. Agreed this is a good time to transition this test file to pytest if @megies is up for it.

[megies]

The reason the mix exists is because we are transitioning from unittest to pytest. Agreed this is a good time to transition this test file to pytest if @megies is up for it.

I might do a separate PR for this