It seems, that this was a problem with Sphinx 1.4.5 (still in testing). With 1.4.6 (unstable), I could build the package again, as with 1.4.4.
- Bug#832854: python-restless: FTBFS: RuntimeErro... W. Martin Borgert
- Bug#832854: marked as done (python-restles... Debian Bug Tracking System
