Make a class new-style (derive from object)

Otherwise super() fails.

Not necessary with Python 3, but necessary with Python 2
(where classic classes are the default

library/blivet.py

@@ -128,7 +128,7 @@ class BlivetAnsibleError(Exception):
     pass
 
 
-class BlivetVolume:
+class BlivetVolume(object):
     def __init__(self, blivet_obj, volume, bpool=None):
         self._blivet = blivet_obj
         self._volume = volume