In response to a DTS request, I was trying to determine if a bug I reported was still in Sierra. I Installed Sierra on a thumb drive, rebooted, launched XCode 7.3.1, tried to run my code. It wouldn't codesign. I tried "fix" and ended up with a dialog with an option to "reset". Turns out that that action revoked my developer certificate. Now I get an email from Apple saying I will have to regenerate all my provisioning profiles. $%U&*!
Nowhere was I warned that "reset" was equivalent to "revoke certificate".
(Apparently, the text bots here did not like my use of the word "h-e-l-l" in the title.)
So much for Sierra making codesigning easier.