Description
matplotlib 3.1.0 removed the aspect kwarg from axes3D and now raises a NotImplementedError (see matplotlib/matplotlib#1077). This broke surface plots in nilearn and the code in code/notebooks/main/brains.ipynb no longer runs.
This is apparently fixed on the master branch of https://github.com/nilearn/nilearn, but the fix hasn't been released yet (see https://neurostars.org/t/plot-surface-error-it-is-not-currently-possible-to-manually-set-the-aspect-on-3d-axes/4852).
I'd suggest we change the Dockerfile to install nilearn from the github page rather than downgrade the pinned matplotlib version and have to A) make sure that works with all other packages' dependencies, and B) regenerate all the figures to make sure none of the output formats changed