Why can't I cast music from python

Configuration
1

I have other pythonscripts that work just fine. This work fine:

- service: media_player.play_media
  data:
    entity_id: media_player.bicameral
    media_content_id: http://my.url:8123/local/goodmorning2.mp3
    media_content_type: 'audio/mp3'

But when I try to do it with python:

service_data = {
  'entity_id': 'media_player.bicameral',
  'media_content_id': 'http: //my.url:8123/local/goodmorning2.mp3',
  'media_content_type': 'audio/mp3'
}
logger.error(service_data)
hass.services.call("media_player", "play_media", service_data)

The chromecast turns on but goes to idle. This happens for example when the url you are passing is a 404, but in this case, I have no idea why it happens.

2

Ha! Blankspace in url!