plugin XEP-0465: log a warning and return empty list/dict when forbidden error is received:

this error probably means that the service doesn't support PPS.

sat/plugins/plugin_xep_0465.py

@@ -20,6 +20,7 @@ from typing import Optional, List, Dict, Union
 
 from twisted.words.protocols.jabber.xmlstream import XMPPHandler
 from twisted.words.protocols.jabber import jid
+from twisted.words.protocols.jabber import error
 from twisted.words.xish import domish
 from zope.interface import implementer
 from wokkel import disco, iwokkel
@@ -50,6 +51,10 @@ NS_PPS = "urn:xmpp:pps:0"
 NS_PPS_SUBSCRIPTIONS = "urn:xmpp:pps:subscriptions:0"
 NS_PPS_SUBSCRIBERS = "urn:xmpp:pps:subscribers:0"
 SUBSCRIBERS_NODE_PREFIX = f"{NS_PPS_SUBSCRIBERS}/"
+NOT_IMPLEMENTED_MSG = (
+    "The service at {service!s} doesn't seem to support Pubsub Public Subscriptions "
+    "(XEP-0465), please request support from your service administrator."
+)
 
 
 class XEP_0465:
@@ -139,9 +144,16 @@ class XEP_0465:
         """
         if service is None:
             service = client.jid.userhostJID()
-        items, __ = await self.host.plugins["XEP-0060"].getItems(
-            client, service, NS_PPS_SUBSCRIPTIONS
-        )
+        try:
+            items, __ = await self.host.plugins["XEP-0060"].getItems(
+                client, service, NS_PPS_SUBSCRIPTIONS
+            )
+        except error.StanzaError as e:
+            if e.condition == "forbidden":
+                log.warning(NOT_IMPLEMENTED_MSG.format(service=service))
+                return []
+            else:
+                raise e
         ret = []
         for item in items:
             try:
@@ -204,9 +216,16 @@ class XEP_0465:
 
         subscribers_node = self.getPublicSubscribersNode(nodeIdentifier)
 
-        items, __ = await self.host.plugins["XEP-0060"].getItems(
-            client, service, subscribers_node
-        )
+        try:
+            items, __ = await self.host.plugins["XEP-0060"].getItems(
+                client, service, subscribers_node
+            )
+        except error.StanzaError as e:
+            if e.condition == "forbidden":
+                log.warning(NOT_IMPLEMENTED_MSG.format(service=service))
+                return {}
+            else:
+                raise e
         ret = {}
         for item in items:
             try: