I also tried to add the PPA again and ran apt-get update. W: The repository ' yakkety Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. W: GPG error: stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1F3045A5DF7587C3 N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository ' stable InRelease' is not signed.