Use python-opencv-headless, add tests
Fixes #1881 (closed). It seems to decrease the container image slightly: 608 MiB -> 596 MiB
Also add some more testing to this code (still playing with new coverage features).
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Fixes #1881 (closed). It seems to decrease the container image slightly: 608 MiB -> 596 MiB
Also add some more testing to this code (still playing with new coverage features).