I was able to find a workaround that seems to resolve the issue.
I discovered that there are alternate versions of the simulation code:
http://first.wpi.edu/FRC/roborio/mav...on/simulation/
so I deleted the simulation directory and then recreated it using the most recent version simulation-2017.2.1.zip
mkdir ~/wpilib/simulation
unzip ~/Downloads/simulation-2017.2.1.zip -d ~/wpilib/simulation
after I moved the files to the new simulation directory, I attempted to rebuild gz_msgs it wouldn't work with gazebo6 so i installed gazebo7 and then rebuilt the gz_msgs
sudo apt-get install gazebo7
move to ~/wpilib/simulation/gz_msgs
mkdir build
cd build
cmake ..
make install
I opened Eclipse. I deleted my GearsBot project and recreated it. Everything worked!