Trajectory demo got error

[liqsuq]

I built this project by "catkin build" and tried samples. But I found following error in "roslaunch rexrov2_gazebo start_demo_pid_controller.launch" on the page of Path and trajectory generators. The purple line was not shown and UUV couldn't be controlled.

Traceback (most recent call last):
  File "/home/xavier/catkin_ws_python3/src/uuv_simulator/uuv_control/uuv_trajectory_control/scripts/rov_pid_controller.py", line 16, in <module>
    import rospy
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/__init__.py", line 49, in <module>
    from .client import spin, myargv, init_node, \
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/client.py", line 52, in <module>
    import roslib
  File "/opt/ros/melodic/lib/python2.7/dist-packages/roslib/__init__.py", line 50, in <module>
    from roslib.launcher import load_manifest
  File "/opt/ros/melodic/lib/python2.7/dist-packages/roslib/launcher.py", line 42, in <module>
    import rospkg
ModuleNotFoundError: No module named 'rospkg'
[rexrov2/rov_pid_controller-12] process has died [pid 20151, exit code 1, cmd /home/xavier/catkin_ws_python3/src/uuv_simulator/uuv_control/uuv_trajectory_control/scripts/rov_pid_controller.py odom:=pose_gt trajectory:=dp_controller/trajectory input_trajectory:=dp_controller/input_trajectory waypoints:=dp_controller/waypoints error:=dp_controller/error reference:=dp_controller/reference thruster_output:=thruster_manager/input_stamped __name:=rov_pid_controller __log:=/home/xavier/.ros/log/0a62de3c-a14b-11e9-84ea-00044bcbaeb2/rexrov2-rov_pid_controller-12.log].
log file: /home/xavier/.ros/log/0a62de3c-a14b-11e9-84ea-00044bcbaeb2/rexrov2-rov_pid_controller-12*.log

I thought the cause is that rov_pid_controller.py's shebang specify Python3. Then I modified following.

.../src/uuv_simulator/uuv_control/uuv_trajectory_control/scripts/rov_pid_controller.py:
- #!/usr/bin/env python3
+ #!/usr/bin/env python

I look like this scripts works for Python2.7 without problems.

This shebang was modified at commit: 79fa8bbb5f9ba37930e6ac4983d5c8035d22191d 8days ago. The commits modified some python scripts' header. However, the shegang's change is toward only rov_pid_controller.py.

This scripts occurs serious problems without using Python3? If so, I must look for other arrpoach. Would you have some ideas?

Thanks for reading.

[pxalcantara]

@musamarcusso Could you take a look ?!