The docs show this:
When copying the example theme supplied with ownCloud in apps/theme-example, make sure that you delete appinfo/signature.json. If you don’t, when you make changes, an integrity warning will be triggered, as the original theme is signed. This is slightly complicated by the fact that without the file a warning will be displayed. However, this is to be corrected in the next release, 10.0.3.
But I've got 10.0.4.4 Community Edition and I'm still getting this warning.
Also, the link that explains how to sign leads to a 404.
So, what's a guy to do?