"Failure to create room" on login when Riot creates a chat with riot-bot, but the homeserver has a federation whitelist

[turt2live]

The config for this homeserver doesn't permit it to talk to matrix.org, and therefore fails to create the room for riot-bot.

[lampholder]

Yuk. I think we really need a Synapse api that exposes all of its configuration settings that a client might care about (such as whether it supports federation).

Do we get a specific 'federation denied' error mesage from Riot's attempt to automatically initiate a chat with riot bot? Anything that could let us provide a better error (or swallow it entirely in the riotbot case?)

[aaronraimist]

Duplicate of #4062

Could probably just edit the title of that issue to be a little less specific as this also affects any failed invite, not just Riot bot. Currently you can reproduce by attempting to start a chat with @tleydxdy:mt.tlebear.win(matrix-org/synapse#4098)