As noted in 27cb099c82, import translators should be rewritten to return
a promise from doImport() and wait for promises from successive
item.complete() calls. They should then be marked as minVersion: "5.0"
to be handled properly by this new code.
(But this tries to account, albeit with somewhat worse behavior, for
translators that haven't been rewritten and sandboxes without Promise
(which is currently the case with child sandboxes in the client).)
(Oh, and I haven't tested this at all in the connectors.)
7c25093ca2