'Handle a m.presence_deny EDU. Removes a local or remote user from a
local user\'s presence list.
Args:
observed_user(UserID): The local or remote user to remove from the
list.
observer_user(UserID): The local owner of the presence list.
Returns:
A Deferred.'

@defer.inlineCallbacks
def deny_presence(self, observed_user, observer_user):

    (yield self.store.del_presence_list(observer_user.localpart, observed_user.to_string()))
