Comment 5 for bug 1369986

This came up again, as I just wanted to play with openid connect, and was forced to install pysaml2 if I had the federation extension enabled. This was discussed in IRC, and we determined that we could either a) attempt to import the pysaml2 modules where it's used, and catch import errors, like in https://review.openstack.org/#/c/145697/1 or b) force the user to install all federation related libraries. I think we are leaning toward b) as it's a more complete solution.