Xcode 8 "the aps-environment entitlement is missing from the app's signature" on submit

Very easy actually. For some reason it got disabled on Xcode 8 but go to Targets -> Capabilities and verify Push Notifications is all correct on that view. For me it had a "Fix Me" I had to click, and voila.

I also have the same problem, and I'm sure Push notification is off by default in Xcode8. I didn't notice it. Be careful about it.

There was a change in Xcode 8, where your entitlements no longer come from the App Identifiers, but from the capabilities selected in your app target. So, like Unome (the OP) said, you have to verify that Push Notifications is switched on.

For me, it wasn't a "Fix Me" button, but I had two entitlement files (one for development and one for distribution). Toggling the Push Notifications capability would add the aps-environment key - with the value development - to the development entitlements file, but it wouldn't add it to the distribution entitlements file. Copying the same key over to distribution worked to get rid of the warning email when uploading to iTunes Connect.

For most projects, it should be sufficient to toggle on Push Notifications, or if it's already on but the key isn't in the entitlements, try toggling it off and on again.

It's also worth noting that entitlements automatically get updated during archive. ie the entitlements generated for release builds can be different from entitlements generated for development builds. See here

During the app distribution process through the Xcode Organizer > Archives tab, entitlements are set onto the app by way of the provisioning profile used for code signing. It is important to be aware that the re-application of entitlements at this phase creates the opportunity for unintended entitlement differences between any prior development builds you may have tested. The primary purpose of this document is to verify that your entitlements are correct for your distribution builds for beta testing and App Store submission.