Hi everyone, exarkun spotted a regression in the 16.0.0 prereleases, where calling endpoints' serverWithString with a SSL strports description and an empty chain file would give an unhelpful error message. These issues have been fixed and are in Twisted 16.0.0pre3. You can find it and the NEWS file at https://twistedmatrix.com/Releases/pre/16.0.0pre3/ . If no further issues are identified, Twisted 16.0 will be released this week (for real!). - Amber Brown Twisted Release Manager