Comment 17 for bug 1592749

I've seen such issues pop up before with apparmor, unfortunately; profiles being left in a halfway state when testing with rapidly installing/uninstalling various packages.
It might be simple to fix, though, as I think I've cleared this up before:
Is there an etc/apparmor.d/usr.sbin.mysqld file? If so, try just deleting it and running sudo /etc/init.d/apparmor reload