解决方案：gazebo-2] process has died [pid 28003, exit code 255, cmd /opt/ros/indigo/lib/_cchangcs

在运行gazebo的过程中，出现了 黑屏 和下面的错误：

[gazebo-2] process has died [pid 28003, exit code 255, cmd /opt/ros/indigo/lib/gazebo_ros/gzserver worlds/empty.world __name:=gazebo __log:=/home/exbot/.ros/log/3bd6002c-c882-11e8-8b6c-000c299fff92/gazebo-2.log].
log file: /home/exbot/.ros/log/3bd6002c-c882-11e8-8b6c-000c299fff92/gazebo-2*.log
[gazebo-2] proce