pubsub response missing its <items> element when no <item> child
According to http://xmpp.org/extensions/xep-0060.html#subscriber-retrieve-error-items the response to an item request should contain the <items> element, even when there's no <item> child to countain.
sat_pubsub with RSM doesn't behave right. To reproduce you can run the tests on sat.src.tmp.wokkel.test.test_rsm. The method test_itemsCount will fail with:
File "/home/souliane/workspace/tmp_packages/sat/tmp/wokkel/rsm.py", line 391, in cb
for element in pubsub_elt.items.elements(pubsub.NS_PUBSUB, 'item'):
exceptions.AttributeError: 'NoneType' object has no attribute 'elements'
pubsub_elt.items should be None event if there's no element.