If the client can't be found synapse fails and reports

Could not find webclient

on the console.
However nothing is reported in homeserver.log except info messages, and they all appear to be normal and expected.

Specifically this occurs on the debian package 0.18.5-1 but I'd expect it to be a general issue.

The same problem also occurs if twisted can't listen on a port (eg: 443)

twisted.internet.error.CannotListenError: Couldn't listen on any:443: [Errno 13] Permission denied.

Appears on the console, but nothing in the logs