Error in tutorial

**Original report ([archived issue](https://osrf-migration.github.io/gazebo_tutorials-gh-pages/#!/osrf/gazebo_tutorials/issues/87)) by Anonymous.**

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In this part of the tutorial:

    Within the same MYROBOT_description**/launch** folder, edit the MYROBOT.world file with the following contents:

there's no launch file inside myrobot_description folder.
