ModuleNotFoundError: No module named 'pymavlink'

If the error as below occurs,

 

$ ../Tools/autotest/sim_vehicle.py --map --console
Traceback (most recent call last):
  File "../Tools/autotest/sim_vehicle.py", line 31, in <module>
    from pymavlink import mavextra
ModuleNotFoundError: No module named 'pymavlink'

 

 

You can uninstall the existing gym and then should install it.
This error appears to be a version problem of gym.

$ python -m pip install pymavlink

 

Next,

 

cd ~/ardupilot/Tools/autotest
$ python sim_vehicle.py --map --console
$ python sim_vehicle.py -v ArduCopter --map --console