cubicweb #542284 display an understandable message when trying to perform a WF transition when someone just did the same [open]

In logilab.org cw-forge (but i guess this is a cw behaviour), I just tried to close a ticket which had been closed a few seconds before by someone else. It resulted in an error message like:

please correct the following errors: by transition: transition isn't allowed
done #8533: push hgview into debian official repositories [resolved]

status will change from resolved to validation pending

please correct the following errors: by transition: transition isn't allowed

Displaying however the editor for commenting the wf transition. CW should display an understandable message instead of this weird messages.

prioritynormal
typebug
done in<not specified>
load0.200
load left0.200
closed by<not specified>