I only recently heard about this.. we fixed that problem in the (current) foolscap-0.9.1 release, made on 21-Sep-2015. Upgrading to 0.9.1 ought to resolve this FTBFS.
(there is a new problem that involves a bad interaction between foolscap-0.9.1 and twisted >=15.3.0, but for teh most part it only affects Tahoe-LAFS. I'm working on a new foolscap release that will resolve it, but I don't think that's cause to hold up putting foolscap-0.9.1 into sid). cheers, -Brian
