An expired CSRF token is reported as a naming convention problem in the image style administration

Problem

The name validation request of the image style administration sends a CSRF token. Once that token has expired, the entity name validation page answers 401, and the administration handles that answer like any other - blaming the naming conventions for a problem that is in fact an expired token.

Steps to reproduce

• Go to Administration / Content / Image Styles
• Leave the page open long enough for the CSRF token to expire
• Type a name in the "New Image Style" field

Actual result

The administration reports a naming convention problem, which is misleading. Creating the style would be rejected for the same expired token, but nothing says so.

Expected result

The administration tells the user that the page has to be reloaded, and keeps the creation button disabled since the creation itself would be rejected too.