Show a warning when viewing a non-public add-on

Describe the problem and steps to reproduce it:

As an admin, log in to AMO and view the detail page for a disabled add-on

or

As a developer, upload an add-on, make it non-public, log in to AMO and view its detail page

What happened?

You see a complete detail page as if nothing was different

What did you expect to happen?

You should see a warning saying that the add-on is not public but you’re seeing it anyway because you have elevated privileges.

Anything else we should know?

This has created confusion a couple of times from admins or developers who are not expecting to see a public listing.

It should be pretty easy to fix:

diff --git a/src/amo/components/Addon/index.js b/src/amo/components/Addon/index.js
index a2d4eec21..52e2b4d4e 100644
--- a/src/amo/components/Addon/index.js
+++ b/src/amo/components/Addon/index.js
@@ -53,6 +53,7 @@ import Card from 'ui/components/Card';
 import Icon from 'ui/components/Icon';
 import LoadingText from 'ui/components/LoadingText';
 import ShowMoreCard from 'ui/components/ShowMoreCard';
+import Notice from 'ui/components/Notice';
 
 import './styles.scss';
 
@@ -537,6 +538,11 @@ export class AddonBase extends React.Component {
                 reason={compatibility.reason}
               />
             ) : null}
+            {addon && addon.status !== 'public' ? (
+              <Notice type="error">
+                {i18n.gettext('This is not a public listing. You are only seeing it because of elevated permissions.')}
+              </Notice>
+            ) : null}
             <header className="Addon-header">
               {this.headerImage({ compatible: isCompatible })}
 

[willdurand]

Do we want both errors?

Yes, that’d be nice.

Do we care about styles here?

Yes, the minimum is to have some padding below the second notification.

[ioanarusiczki]

I’m adding that the message is also available for developers before the add-ons are auto-approved or approved by admins. Verified on AMO stage with FF61(Win10)