Until now, rbt post with the submit-as option could not update unpublished review requests. I've proposed that users with the can_submit_as_another_user permission are allowed to list unpublished review requests, so that rbt post knows about these and can update them. Previously only superusers could list unpublished review requests.

Expanded unit test to test that can_submit_as_another_user gives user access to unpublished review requests
Tested with rbt post -u --submit-as=submitter to update unpublished review request (see also #7195)