Could not wake up Gazebo. [firefly/hovering_example-7] process has died

[kpiyush25]

Getting this error while launching a node named dock_detector using roslaunch dock_detector default.launch

• [FATAL] [1598170671.089197390]: Could not wake up Gazebo. [firefly/hovering_example-7] process has died [pid 11236, exit code 255, cmd /home/username/ros_ws3/devel/lib/rotors_gazebo/hovering_example __name:= hovering_example __log:=/home/username/.ros/log/1b5faae0-e519-11ea-9254-d0abd521f44e/firefly-hovering_example-7.log]. log file: /home/username/.ros/log/1b5faae0-e519-11ea-9254-d0abd521f44e/firefly-hovering_example-7*.log

[kpiyush25]

Initially we used to specify the model path for the custom models that were used from iarc_simulation_tools inside the launch file itself but as we moved we encountered some clashes due to the path. We found that after removing the model path from launch file and including it inside the bashrc sorts out the problem and hence we did the same.
So the line that I added inside bashrc to resolve it was:
export GAZEBO_MODEL_PATH=${GAZEBO_MODEL_PATH}:~/iarc_ws/src/IARC2020/iarc_simulation_tools/iarc_simulation_tools/models
So after specifying the model path ,the above error was resolved.