https://core.trac.wordpress.org/ticket/49587
This ticket will enable us to show an error message to the user if there is a problem connecting to the asset provider. Currently WP core does not handle an error being returned from the attachments query, and any error results in the eternal spinner of doom.
I started working on this in WordPress/wordpress-develop#1065 but I forgot how difficult it is to figure out the media manager views. If someone wants to pick this up and carry on with it that would be great.