Fix Python 3 failure in automodsumm

I'm confused by this part.  It looks to me like in a commit a few days ago you changed it from ``self.arguments = [u' '.join(clsnms)]`` to ``self.arguments = [' '.join(clsnms)]``.  So doesn't that break in py 2.x if you don't have ``from __future__ import unicode_literals`` at the top?  Or am I misunderstanding what problem this was supposed to solve?