bitbake/runqueue.py: Drop duplicated class

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

bitbake/lib/bb/runqueue.py

@@ -28,12 +28,6 @@ import signal
 import stat
 import fcntl
 
-class TaskFailure(Exception):
-    """Exception raised when a task in a runqueue fails"""
-    def __init__(self, x):
-        self.args = x
-
-
 class RunQueueStats:
     """
     Holds statistics on the tasks handled by the associated runQueue