Hi, I'm not sure if it considered a Twisted bug, but Twisted Conch on Twisted 19.2.1 now seems to require explicit installation of bcrypt, which wasn't the case on <19.2.1. Here is our (Crossbar.io) tracking issue: https://github.com/crossbario/crossbar/issues/1555 Not a big deal obviously - we'll add that (indirect) dependency to Crossbar.io .. just wanted to post here if anyone else runs into. Cheers, /Tobias PS: I did test the upcoming Twisted release with Crossbar.io - but only a "quick manual test", not our full CI - which now ran red (by being triggered from an unrelated PR). There is more fallout for us with the new Twisted release:( Analyzing that now. We (Crossbar.io) really should have run our _full_ CI on the upcoming release.