Rest Notify for Discord Webhook 400 Error

Hi All,

As Hassio discord notify currently isn’t working due to the async problem in python 3.7 in (that I can’t find on hassio to update!) (if you can tell me how to find the discord/ file that would help too)

I have followed the work around and created the following rest notify for a webhook on my discord server;

- name: discord_webhook
  platform: rest
  method: POST
  message_param_name: content
  title_param_name: username
    username: Home Assistant
  resource: !secret discord_webhook  

Which is working to post messages. BUT i also get these errors in my log;

2019-04-19 21:06:25 ERROR (SyncWorker_12) [] Client error. Response 400: BAD REQUEST:
NoneType: None

Constantly, as in 1 from a different synworker_xx per second

Can anyone please let me know what I have done wrong, so that I can stop these errors please.