CI build failing at `three_dimensional_image_processing.ipynb`

[matthew-brett]

The deploy CI step appears to be failing - and in fact, has been failing as far back as Github recorded time, which in this case is Oct 13, 2024. We don't have the logs for previous failures, but the current failure is at: https://github.com/scikit-image/skimage-tutorials/actions/runs/19743273036/job/56700535295#step:5:56

/home/runner/work/skimage-tutorials/skimage-tutorials/lectures/three_dimensional_image_processing.ipynb: Executing notebook using local CWD [mystnb]

Exception occurred:
  File "/opt/hostedtoolcache/Python/3.12.12/x64/lib/python3.12/site-packages/nbclient/client.py", line 1009, in async_execute_cell
    raise DeadKernelError("Kernel died") from None

three_dimensional_image_processing.ipynb makes heavy use of Napari - I wonder whether this is due to the headless build - it passes on my system, where the Napari screens are displayed.

I've pushed a gh-pages build manually for now.