The problem is the PyQt4 UUID conflict you reported here:
http://bugs.gentoo.org/show_bug.cgi?id=317557
My system is x86 and I couldn't get any combination of util-linux and PyQt4 to work.
As your example on the bug report shows, it works if the UUID is loaded before PyQt4.
Importing the UUID in calibre's __init__ seems to solve the issue.