Cagou throws exceptions when no avatar is found. It should be handled gracefully because it's not a big dead and it gives the impression that something went wrong.
Can't get avatar: NotFound: Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/dbus/service.py", line 707, in _message_cb
retval = candidate_method(self, *args, **keywords)
File "<DBus bridge>", line 1, in avatarGet
File "/usr/lib/python2.7/site-packages/sat/bridge/dbus_bridge.py", line 107, in _callback
result = self.cb[name](*args, **kwargs)
File "/usr/lib/python2.7/site-packages/sat/plugins/plugin_xep_0054.py", line 397, in _getAvatar
d = self.getAvatar(client, jid.JID(entity), cache_only, hash_only)
File "/usr/lib/python2.7/site-packages/sat/plugins/plugin_xep_0054.py", line 413, in getAvatar
raise exceptions.NotFound
NotFound