Reading package lists... Done
W: GPG error: http://debian.yeasoft.net trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40FC0CD26BF18B15
W: GPG error: http://ppa.launchpad.net trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4874D3686E80C6B7