Partial HTTP downloads using twisted.web.client.Agent

Hi! I need to download a fragment of a file using HTTP. The file is
stored in several hosts, and I need to handle the case where one or
several hosts are down, or do not have a copy of the file, or the
connection fails for any other reason.

Inspired by the Twisted client tutorial
(http://twistedmatrix.com/documents/current/web/howto/client.html),
I've written a function called ``download()``
(http://gist.github.com/481575) which iterates through a list of URLs.
I find the resulting code a bit too long, however -- in particular the
need for the ``FileWriter`` class.

Have I overlooked some Twisted helper code, or some Twisted coding
idiom, that could simplify the example above? Can you guys think of
any way to improve that code fragment?

Thanks a lot,

C