OK this wait I suggested above is still not strong enough. There is more crap going on after even this event and I cannot work out nor find out from devs what is going on.
I suggest let's just add 'time.sleep(5)` and a `TODO` in there and we'll get back to it if we can.
I raised this issue against Persona and its testability:
https://github.com/mozilla/browserid/issues/3318