There was an unplanned server reboot this morning, after which mastodon-web/tootctl were throwing an exception "NameError: uninitialized constant ActiveSupport::Logger::WARNING"
After debugging for a couple hours, blowing away and restoring several times, I finally compared fresh-install environment variables to the production config. That's when I found the spurious var "RAILS_LOG_LEVEL=warning" that I must have forgotten about. Removing that resolved the exception. Derp! Lesson learned..