fixed skimage import

[emmanuelle]

Closes #1826 and #1829

[nicolaskruchten]

So with this we just can’t see certain factories when the deps aren’t installed? Shouldn’t we just throw a call-time error instead? Otherwise someone will try to run the docs and be confused about import failures, no?

[nicolaskruchten]

Or does “optional imports” warn or something?

[emmanuelle]

We can probably import the dep inside the ff function instead, yes. I just copied the behaviour which was used for pandas and county_choropleth, I did not give it much thought

[nicolaskruchten]

💃