minor cleanup in incidence structures

[chapoton]

this ticket aims to

• remove unused import statements in the file combinat/designs/incidence_structures.py

• put this file in a pep8 standard shape

[chapoton]

I am trying the git way of life. Seems to work. Hope I have made everything right.

[ncohen]

Helloooo !!

Well, your patch looks good but your branch contains two commits, the second just fixing a typo. I think that it does not change anything, for if I got everything right your two commits will appear as only one when your patch will be merged into Sage.

This being said, it is very easy to merge (=squash) commits with git, so if you want to give it a try here's how it works : ​http://gitready.com/advanced/2009/02/10/squashing-commits-with-rebase.html

And you can decide whether you want to merge these two commits together, and set this ticket to positive_review on my behalf when you are set :-)

Nathann

[chapoton]

well, thanks for the info about merging commits.

I think I prefer to avoid doing that right now (if this is not needed), but I will try at some other occasion.

So, positive review