Okay thanks! Now I'm able to reproduce it.

I can't reproduce the problem, because MediaWiki assigns a diff number to every small change (protection for example).
The reason for the change is noted in the summary and its saved as a minor edit without any content changes.
And the API action should be feedwatchlist or?

This problem is related to job queues. It depends how fast they can process the update.
That's the reason why I've increased the delay to the refresh to 7,5s.

I've created a solution which reloads the category list after a addition from the server.

Hello @Bawolff @Legoktm @hoo,
it would be nice, if you've got time to look at my change.

I did a little bit of code digging:

With the patch it'll look like this:

When this error during a upgrade happens, it looks like this after the patch:

Thanks for reviewing this so fast. It's really exciting to get code into production although it's just a small change. ^^

Isn't this task completed with https://phabricator.wikimedia.org/T99982?

@Dzahn Was @238482n375 just a hacked account or a bot with evil intentions?

@Aklapper I wanted to do this as a task for the Google Code-in, so I looked at the list of non converted extensions, found this extension and created this task.
Next I visited the extension page and it seemed working (because the page is full of usage instructions), so I cloned it from Gerrit, but when I wanted to convert the extension there was no code. I also checked the other branches, but I couldn't find anything.

Okay there seems to be no code for this extension, so we can't upgrade it to the new registration system.

I marked my stuff as done or in progress