Confusing error message - "%s is not the name of a group chat."
Bug description
I've joined a group chat on Conversations. Somehow Gajim didn't pick up the invitation and I had to join manually.
Unfortunately, all my attempts ended with error "(chat name here) is not the name of a group chat.". The message is completely meaningless to me, it suggests that I made a typo in group chat name or something similar.
After looking up the message in source code, I discovered that the message is printed when (1) the conference JID is already in roster, and (2) the conference JID in roster is not marked as a conference.
I suggest changing:
"%s is not the name of a group chat."
to
"%s is already in your roster and does not look like a group chat."
Optionally with a longer explanation:
"Please check if %s is a correct group chat name. If it is, delete it from your roster and try joining the group chat again."