Taskset failed() result is incorrect (patch)

[foobarto]

Calling failed() on a taskset returns True if some tasks are still pending (it treats pending tasks as failed tasks right now in other words).

Below patch:

--- a/result.py
+++ b/result.py
@@ -85,6 +85,14 @@

         """
         return self.backend.is_successful(self.task_id)
+    
+    def failed(self):
+        """Returns ``True`` if the task failed
+        
+        :rtype: bool
+        
+        """
+        return self.backend.get_status(self.task_id)==states.FAILURE

     def __str__(self):
         """``str(self)`` -> ``self.task_id``"""
@@ -223,7 +231,7 @@
             (i.e., raised an exception)

         """
-        return any((not subtask.successful()
+        return any((subtask.failed()
                         for subtask in self.itersubtasks()))

     def waiting(self):