Fix tests: Not every channel has a closing (especially in tests).

Author: alexsilva

supervisor/xmlrpc.py

@@ -134,7 +134,7 @@ def getresponse(self, body):
         outgoing_producer = producers.composite_producer(self.request.outgoing)
 
         # apply a few final transformations to the output
-        if not self.request.channel.closing:
+        if not getattr(self.request.channel, "closing", False):
             self.request.channel.push_with_producer(
                 # globbing gives us large packets
                 producers.globbing_producer(