Remove every old-style class.

src/plugins/plugin_misc_account.py

@@ -78,7 +78,7 @@ class ProsodyRegisterProtocol(protocol.ProcessProtocol):
             self.deferred.errback("INTERNAL")
 
 
-class MiscAccount():
+class MiscAccount(object):
     """Account plugin: create a SàT + Prosody account, used by Libervia"""
     #XXX: This plugin is a Q&D one used for the demo. Something more generic (and not
     #     only focused on Prosody) is planed