当我apt-get update在 ubuntu-14.04 上使用“ ”更新时，出现以下错误，
W: GPG error: http://packages.osrfoundation.org trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 67170598AF249743
我试过按照某些论坛中给出的命令
apt-key adv --keyserver keyserver.ubuntu.com --recv-key 67170598AF249743
输出如下
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --homedir /tmp/tmp.XI2D9gTkMc --no-auto-check-trustdb --trust-model always --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keyserver.ubuntu.com --keyserver-options http-proxy=http://202.141.80.80:3128 --recv-key 67170598AF249743
gpg: requesting key AF249743 from hkp server keyserver.ubuntu.com
gpgkeys: key 67170598AF249743 not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number …