This is a common problem, my solution does not necessarily apply, but my computer can be solved. Priority replace the mobile phone network and try again.
First, the emergence of this problem, use your browser to view this page:
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list
Found not get in, so naturally no way to download.
The solution is to uninstall the previous installation package:
sudo apt-get remove ros-*
Then reconfigure the source, select ustc source in the software update.
Then enter the console, add USTC source:
sudo sh -c '. /etc/lsb-release && echo "deb http://mirrors.ustc.edu.cn/ros/ubuntu/ $DISTRIB_CODENAME main" > /etc/apt/sources.list.d/ros-latest.list'
Add key:
sudo apt-key adv --keyserver hkp://pool.sks-keyservers.net --recv-key 0xB01FA116
After the procedure the same as before:
sudo apt-get update
sudo apt-get install ros-kinetic-desktop-full
And then perform that step before the problem:
sudo rosdep init
If correct, will return: Wrote etc / ros. . . . (Omitted), this time, if you go before the visit that website, it should be able to go in it
Then, after the execution in accordance with official website. I do not know if I have the solution to your problem then
