Now it triggered an exception, crashing the server. This happens
rarely, and only if a client connection is very slow. As this is
already the fallback of the normal download flow, we are left
with no alternatives: the client cannot download the file via a
more reliable HTTP connection, and is downloading over our TCP
connection in such a slow speed, the S3 backend gives up on it.
The only reasonable thing to do, is to drop the connection to
the client on our end too.

For development this is useful, meaning you don't need a full
library in order to debug the server.