Bug#848112: Python-skimage depends on unavailable package python-dask

[Stefan van der Walt]

I would have absolutely no problem moving skimage to team maintenance. 
If Yarik agrees, I'd appreciate some pointers on how to move forward
with that.  What I would like is to remain in the loop w.r.t. packaging
changes.  python-dask should be packaged now, I think Diane Trout of one
of the teams has been working on that the past week.