core (disco): added checkFeature method + fixed hasFeature test

src/memory/disco.py

@@ -18,6 +18,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from sat.core.i18n import _
+from sat.core import exceptions
 from logging import debug, info, warning, error
 from twisted.words.protocols.jabber import jid
 from twisted.internet import defer
@@ -67,6 +68,22 @@ class Discovery(object):
         @return: a Deferred which fire a boolean (True if feature is available)
         """
         disco_info = yield self.getInfos(jid_, profile_key)
+        defer.returnValue(feature in disco_info.features)
+
+    @defer.inlineCallbacks
+    def checkFeature(self, feature, jid_=None, profile_key=C.PROF_KEY_NONE):
+        """Like hasFeature, but raise an exception is feature is not Found
+
+        @param feature: feature namespace
+        @param jid_: jid of the target, or None for profile's server
+        @param profile_key: %(doc_profile_key)s
+        @return: None if feature is found
+
+        @raise: exceptions.FeatureNotFound
+        """
+        disco_info = yield self.getInfos(jid_, profile_key)
+        if not feature in disco_info.features:
+            raise exceptions.FeatureNotFound
         defer.returnValue(feature in disco_info)
 
     @defer.inlineCallbacks