handle errors from celery backend
meant to return QueueError, not raise it
include command in header, if available
configure header names as attrs
use a blocking deque instead of PriorityQueue
full test coverage of BlockingDeque
removed unnecessary yield
Merge branch 'master' into outbound_http
renamed logging module
renamed logging module from wsgi to http
Merge branch 'outbound_http' of github.com:icgood/python-slimta into outbound_http