Heroku Redis is removing the 'h' username for connection urls
Change effective on 09 October 2020
In the past Heroku Redis passed a place holder username of h because some clients could not correctly handle a blank username in the URL. After the release of ACLs in Redis 6, clients began to support the new AUTH command that uses 2 arguments (username and password). Clients that attempt to pass the h username to the AUTH will result in an error on Redis versions 4 and 5.
AUTH failed: ERR wrong number of arguments for 'auth' command.
To correct this issue, Heroku does not pass the h username on Redis 6 and has begun to remove the h username from connection URLs on version 4 and version 5 as well. The change to version 4 and version 5 will roll out over the next 2 weeks, only to new addons. Existing addons will not have the h username removed.