scikit-image & nibabel dependencies

[pandas-a11y-11]

Is scikit-image a runtime dependency, or does it only need to be present in the target system to build plugins? Same question for nibabel.

[tfmoraes]

Hi @pandas-a11y-11. scikit-image is used in the watershed tool and in the deeplearning segmentation tools. nibabel is used to open nifti images and to export to nifti.