Typo(?) in general_examples_algebra.py, example 23.

[javimixet]

I had to change code in line 389 from sk23 = make_face(l1, l2) to sk23 = make_face(l1 + l2) for the revolve to work.

[jdegenstein]

Thanks for reporting! I added to my PR here #715, but I used a slightly different solution: sk23 = make_face([l1, l2]) which I think was probably what was originally intended.