showMollview(): difficulty retrieving colorbar

[willclarkson]

In showMollview(), when running on Datalab using rubin_sim and kernel "LSST-2021.10.13 Py3" (which seems to be required to run rubin_sim), the line retrieving the colorbar,

plt.gca().images[-1].colorbar

now returns None instead of the colorbar object. This might be related to the matplotlib version... the new kernel uses matplotlib version 3.3.4 while the older version uses 3.4.1.

[Thalos12]

It is likely that the issue is caused by version 3.4.0.
In its changelog, several changes to colorbars involving the label are mentioned.