Firstly, thank you for this nice library.

I have a problem with only some specifics URLs :
When I have a bad network conditions, I get incomplete download, and the image is not stored in cache :

The header of the URL of the image :

Cache-Control → private
Connection → keep-alive
Content-Length → 94896
Content-Type → image/jpg
Date → Tue, 12 Jan 2016 14:21:14 GMT
Expires → Thu, 11-Feb-2016 14:21:13 GMT
Pragma → cache
Server → Rocket 1.2.6 Python/2.7.3
X-Powered-By → web2py

Example of URL : http://preprod.verybuzzy.com:8000/bitc/Webservice_Media/getUserPhoto/1/58/1

Have you any idea what it is this bug?
Thank you