Hi
I encountered a similar issue as @amiralavi. As I was not content with the Mapbox graphs for dash, I tried to create my own component using Leaflet. I first worked with React-Leaflet. My code worked fine when I was just running the react/JS code using npm run start. However, when I built the python package and tried starting python usage.py, I got the “Error loading dependencies” message. Looking into the console I found that my external libraries were not included by webpack, even though it was included in the packages.json.
@chriddyp: Unfortunately, also the new tutorials for D3 were not really helpful. I downloaded the example from Github and was able to run it without any issues. However, taking a similar approach with React-Leaflet did not resolve the issue. I will therefore open up an issue on Github and hope you can look into that sometime.
Cheers