We’re looking at this, yes.
In the meanwhile as a workaround in a container you can backrev your postgresql-client-9.5 packages to below 9.5.12 (or below 10.3) and the backup will work.
More or less: under the hood we restore to the restore schema and then atomically switch that to the public (production) schema so that the site is “up” during the restore. But these new versions of pg_dump generate a script that explicitly refers to the public schema… 
restore fails.