错误提示：
WARNING:root:could not open file '/etc/apt/sources.list不小心把源文件删除了，不能更新，下载，和卸载软件了。搞了半天实在无解，最后，拷了同学的sources.list文件，放到原处，解决。
错误提示：
WARNING:root:could not open file '/etc/apt/sources.list.d/mystic-mirage-ubuntu-pycharm-xenial.list'
WARNING:root:could not open file '/etc/apt/sources.list.d/xenial-partner.list'
WARNING:root:could not open file '/etc/apt/sources.list.d/chromium-daily-ubuntu-ppa-xenial.list'
WARNING:root:could not open file '/etc/apt/sources.list.d/sogoupinyin.list'
WARNING:root:could not open file '/etc/apt/sources.list.d/bazel.list'
WARNING:root:could not open file '/etc/apt/sources.list.d/google-chrome.list'
WARNING:root:could not open file '/etc/apt/sources.list.d/graphics-drivers-ubuntu-ppa-xenial.list'
在终端输入
sudo chmod +x /etc/apt/sources.list.d解决！