I just upgraded from an April 2007 SVN version of twisted web2 to 8.0, and I started getting some errors from my client streams. The errors don't really seem to be errors though, as they only indicate that the connection was closed properly, which it is supposed to be.
I'm not sure if this "error" is something I should be handling myself, or if there is some defect in web2 since maybe it should handle this situation itself.
I traced the change that is causing this to changeset 21366:
where I think the relevant change is the new call to stream.finish() added to the _error() function. Perhaps _error() or stream.finish() should be handling ConnectionDone errors?