Well, no, it seems like nothing is happening. Nothing happens when running MigrateUploadScheme and there are no sidekiq jobs queued.
root@shadrack-rbx:/var/www/discourse# rake uploads:migrate_to_s3
Migrating uploads to S3 for 'default'...
Some uploads were not migrated to the new scheme. Please run these commands in the rails console
SiteSetting.migrate_to_new_scheme = true
Jobs::MigrateUploadScheme.new.execute(nil)
root@shadrack-rbx:/var/www/discourse# rails c
[1] pry(main)> SiteSetting.migrate_to_new_scheme = true
=> true
[2] pry(main)> Jobs::MigrateUploadScheme.new.execute(nil)
=> []