Issue Overview

Gutenberg version 1.7.0
When a contributor uses Gutenberg he can use Image relative blocks. When he tries to use it as this role hasn't got the upload_files capability, the REST reply to site.url/wp-json/wp/v2/media is rest_cannot_create (403).

Steps to Reproduce (for bugs)

1. Log in as a contributor.
2. Add a new post.
3. Select the image block.
4. Upload an image.
5. The image shows for a few milliseconds.
6. The Upload/Browse buttons are replacing the vanished image.
7. No feedback is provided to the contributor untill the automatic save feature run. Then the error is: "This block has encountered an error and cannot be previewed."

Chrome Version 62.0.3202.94

Expected Behavior

Image/files relative blocks should only show if ( current_user_can( 'upload_files' ) )

Current Behavior

Image/files relative blocks are showing no matter the "upload_files" capability of the logged in user.

Possible Solution

Screenshots / Video

Here is some oxygen 😉 https://cldup.com/K8qYyaHWbI.mp4

Related Issues and/or PRs

Todos

• Tests
• Documentation