The error state for the file picker is not clear and not consistent with the other fields.

Whilst all fields in an invalid state are highlighted with a red border, display an exclamation mark icon and a message below the field, the file picker is not highlighted and it is not immediately clear that an error message is shown.

As the invalid state is not evident, some users may not be able to locate the error message alone and may be unable to submit the form.

Steps to reproduce

• Login as an administrator
• Go to "site settings" > "upload course" (/admin/tool/uploadcourse/index.php)
• Note that the file upload field is required
• Leave the field empty and submit the form
• Note that error message is not easy to spot and that the field is not highlighted in red

Expected behavior

The field is highlighted with a red border, an error icon, and the error message is shown following the same convention that is used in with other fields.