collaboration: handle tubes channel failure gracefully

CHANNEL_TYPE_TUBES was deprecated since telepathy-gabble 0.17.25 and
is no longer present on modern distributions. This breaks collaboration
for _all_ activities, regardless if they use tubes or not.

Therefore, check if the channel creation failed due to support and allow
channel creation process to continue.

This patch fixes collaboration for the activities that do not use tubes
channel in modern distributions, but also allow to use tubes when running
on older distributions.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>

src/sugar3/presence/activity.py

@@ -554,6 +554,7 @@ class _JoinCommand(_BaseCommand):
         self._finished = False
         self.room_handle = room_handle
         self._global_self_handle = None
+        self._tubes_supported = True
 
     def run(self):
         if self._finished:
@@ -581,7 +582,7 @@ class _JoinCommand(_BaseCommand):
             self.room_handle,
             True,
             reply_handler=self.__create_tubes_channel_cb,
-            error_handler=self.__error_handler_cb,
+            error_handler=self.__tubes_error_handler_cb,
             dbus_interface=CONNECTION)
 
     def __create_text_channel_cb(self, channel_path):
@@ -592,6 +593,15 @@ class _JoinCommand(_BaseCommand):
         Channel(self._connection.requested_bus_name, channel_path,
                 ready_handler=self.__tubes_channel_ready_cb)
 
+    def __tubes_error_handler_cb(self, error):
+        if (error.get_dbus_name() ==
+                'org.freedesktop.Telepathy.Error.NotImplemented'):
+            self._tubes_supported = False
+            self._tubes_ready()
+        else:
+            self._finished = True
+            self.emit('finished', error)
+
     def __error_handler_cb(self, error):
         self._finished = True
         self.emit('finished', error)
@@ -608,7 +618,7 @@ class _JoinCommand(_BaseCommand):
 
     def _tubes_ready(self):
         if self.text_channel is None or \
-                self.tubes_channel is None:
+                (self._tubes_supported and self.tubes_channel is None):
             return
 
         _logger.debug('%r: finished setting up tubes' % self)