Dead link to test data (used in Jupyter notebook)

[henrykrumb]

When opening the Jupyter notebook (deepdrr_demo in project directory, main branch), it fails to load the test dataset and breaks by raising a BadZipFile: File is not a zip file exception.

The same thing happens when the notebook is opened and executed in Google Colab.

Apparently, the dataset downloaded by deepdrr.utils.test_utils.download_sampledata("CTPelvic1K_sample") does not exist anymore, hence the data cannot be loaded properly. In the source code, there

I suggest the following changes:

1. Update or remove reference to pelvic dataset in deepdrr.utils.test_utils
2. In the Jupyter notebook example and colab, use "CT-chest" data (which is hosted by 3D Slicer, and can be expected to remain on their servers)
3. In deepdrr.utils.test_utils.download_sampledata, make the error messages / exceptions more descriptive. If a file cannot be downloaded due to 404, it should be displayed as such and fail before attempting to unzip.

[Edit 1]: A PR was created for item 2. on the list (PR #95)