When the visibility timeout of a message expires before we've managed to extend it, then
the ChangeMessageVisibility request will throw a MessageNotInflightException
.*
#x9 | #xA | #xD | [#x20 to #xD7FF] | [#xE000 to #xFFFD] | [#x10000 to #x10FFFF]
(see http://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessage.html)