core (memory/disco): fixed checkFeature return Failure:

it seems that instanciating a Failure with a class name is not working anymore, so the
exceptions.FeatureNotFound is instanciated now.

sat/plugins/plugin_misc_text_commands.py

@@ -371,12 +371,12 @@ class TextCommands(object):
         whois_msg = [_("whois for %(jid)s") % {"jid": target_jid}]
 
         d = defer.succeed(None)
-        for ignore, callback in self._whois:
+        for __, callback in self._whois:
             d.addCallback(
-                lambda ignore: callback(client, whois_msg, mess_data, target_jid)
+                lambda __: callback(client, whois_msg, mess_data, target_jid)
             )
 
-        def feedBack(ignore):
+        def feedBack(__):
             self.feedBack(client, "\n".join(whois_msg), mess_data)
             return False