Report access denied error from DLQ

[SpectralHiss]

Firstly i'd like to say thanks so much for this tool, saved me a lot of time/effort there.

One thing that could be slightly improved is that judging by logic if receive message returns 0 messages , regardless of whether it's because it was an empty receive or an access denied the code just returns..
This even shows that messages X got copied correctly based on estimate even though nothing happens in this case (access denied on DLQ when tested receive manually).

i will try and submit a quick PR to this if time allows