今天尝试安装docker最新社区版，在注册官方安装源的时候遇到问题。
按官方文档所述，已经安装好apt的https模块，下载并验证了证书。执行如下语句注册官方源
sudo add-apt-repository \
"deb [arch=amd64] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) \
stable"
执行后，/etc/apt/source.list如下：
……
deb [arch=amd64] https://download.docker.com/linux/ubuntu trusty stable
# deb-src [arch=amd64] https://download.docker.com/linux/ubuntu trusty stable
……
此时执行更新命令apt-get update，报如下异常
……
Ign https://download.docker.com trusty InRelease
Ign https://download.docker.com trusty Release.gpg
Ign https://download.docker.com trusty Release
Err https://download.docker.com trusty/stable amd64 Packages
Bad header line
Ign https://download.docker.com trusty/stable Translation-en_US
Ign https://download.docker.com trusty/stable Translation-en
Fetched 68.8 MB in 2min 0s (574 kB/s)
W: Failed to fetch https://download.docker.com/linux/ubuntu/dists/trusty/stable/binary-amd64/Packages Bad header line
E: Some index files failed to download. They have been ignored, or old ones used instead.
清除缓存（rm -Rf /var/lib/apt/lists/*）后再次执行更新依然是上述异常。
谁有过类似问题解决经历或者解决思路，请不吝赐教！
