Not enabling ipysankeywidget for nbextension gives nothing

[harmbuisman]

Hi, I found that not running the following line prevents any output with the code in the tutorial, not for the ipysankeywidget example nor for the floweaver example (that I assumed did not depend on the widget package_:

jupyter nbextension enable --py --sys-prefix ipysankeywidget

I can imagine that you will not get output to a notebook, but without that line I also do not get output in the output png file.

Would it be possible to give an informative error or warning when running code without access to the widget? E.g. for the "auto_save_png" call?