Convert to Python 3: `dict.itervalues()` -> `dict.values()`

sznqalibs/hoover.py

 
         def get_all_colnames():
             cn = {}
-            for affected in self._db.itervalues():
+            for affected in self._db.values():
                 for argset in affected:
                     cn.update(dict.fromkeys(argset.keys()))
                 return sorted(cn.keys())