ros2 dashing 安装失败指南

   22  sudo rosdep init #失败
   23  sudo -E rosdep init #查看错误
   24  ls
   25  wget https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list #查看链接
   26  sudo -E rosdep init # 执行成功
   27  sudo -E rosdep update #delete
   28  rosdep update
   29  sudo -E rosdep fix-permissions
   30  rosdep update