Similar to bug #189497, an incompatibility based on a change in twisted.web.client is needed to deluge. It has apparently been committed to deluge 1.3-stable, and will be in 1.3.12.
It looks like 1.3.12 isn't out yet, but pre-applying this patch to the FreeBSD port would be helpful to me at the moment.
I should also note the deluge ticket from where I acquired that link to the change for 1.3-stable:
A commit references this bug:
Date: Tue Mar 10 17:28:25 UTC 2015
New revision: 380945
net-p2p/deluge: fix blocklist plugin
Add upstream patch to fix blocklist plugin with version of Twisted
that's now in ports tree.
Upstream bug report: http://dev.deluge-torrent.org/ticket/2737
Reported by: Chris Ross <firstname.lastname@example.org>
Committed, thank you.