Fix Python 3 failure in automodsumm

Ah I see, I was the one who introduced this issue. I was trying to fix this code for Python 3.2 in 507217e1b329fbec9944e757b47918563cd9638c (because it was raising a syntax error) but in fact it didn't *fix* it in the sense that it ran properly - it just fixed the syntax error. It also didn't change anything for Python 2.x because it was still converting to Unicode. With this PR indeed it is no longer unicode in Python 2. However, it seems to still build properly and in fact this is now covered by the tests. So maybe Sphinx doesn't care if these arguments are unicode. Do you remember why you had included the ``u''`` in the first place?