Worker cannot get next download url if purldb is behind basicauth

I've set up a private instance of purldb, generated a scan queue worker api key, and when I tried connecting the scan queue worker to it, it failed to get the next jobs from purldb.
I set the PURLDB_URL, PURLDB_USER, PURLDB_PASSWORD, and PURLDB_API_KEY environment variables, then in a shell, I was able to use the basic auth credentials to get the package listing. When I tried to visit the `/scan_queue/get_next_download_url/` endpoint, I got a 401.