Foreman 1.11.1: Unable to update puppet environments and classes?

I've recently upgraded to Foreman 1.11.1 on a CentOS 6.7 host with
puppet-3.8.6. I used to be able to import puppet classes with:

su - foreman -s /bin/bash -c 'foreman-rake
puppet:import:puppet_classes[batch] RAILS_ENV=production

But now the Foreman production.log cheerfully says: [app] [W] Failed to
refresh puppet classes: []

Meanwhile, the foreman-proxy appears to be scanning all our proper
directories for modules, classes, and environments while the rake is going
on. Why isn't Foreman ingesting the new data?