Contributor Role can't create a new post using Gutenberg

[ammist]

Issue Overview

Users with the "Contributor" role who use Gutenberg see errors when trying to save new posts (only Publish button is available, no "submit for review")

Steps to Reproduce (for bugs)

1. Log in as a "Contributor" user
2. Click on Gutenberg
3. Add some text to your post
4. Observe that the "Publish" button is lit up.
5. Click on Publish button
6. Note error Message: Publishing Failed.
7. Go to Posts list. The post appears as "draft".

This is using
WordPress 4.8.1
Gutenberg 0.9.0
Firefox browser

Expected Behavior

When adding a new post as a contributor, the "Publish" button should be replaced with "Save Draft" and/or "Submit for Review".
The correct post status should be displayed when editing the post in Gutenberg.

Current Behavior

When adding a new post (or editing using Gutenberg) the "Publish" button appears. Clicking that button saves the post, generating a new revision, and shows an error.

I also tried clicking the switch for "Pending Review", then "publish". Again, the same error.
When I went to the Posts List screen, I see my post as "Pending Review".

Possible Solution

Related Issues and/or PRs

#2029

Todos