If it's trivial to build images yourself, then just build it and be thankful for all the utility you earned by deferring doing the task till later - time is money, very literally, the whole point of credit is time-shifting money. You were allowed to time-shift work, and for free. But the expectation you could time-shift it forever is not based on any promise - they were always free to revoke the option, and now they did. If it's a trivial task, make your own one - you could even do the society a service and put it up on the docker repo.