OPT-OUT of App Signing by Google Play - Andromo Apps are already Signed for you!
Google has added a new optional item in the Google Play Developer Console called "App Signing by Google Play".
Andromo apps are already signed for you by Andromo.
Since you're not signing the app yourself, and don't possess the original signing credentials, you MUST choose OPT-OUT or Google Play will not let you upload your app!
There is no way to "OPT-OUT" later if you choose to continue. The only thing you can do is change the package name of your app and then upload it as a new app.
This is only for new apps, the first time you add them to Google Play. It does not show up for existing app updates (since you can never change a signing key), so you will only need to do this the first time you add an app to Google Play.