Python module not found when launched in cron

I am running a little ubuntu server (version 18.04)

Before upgrading to 18.04 the cron was executing just fine.

This is my crontab (sudo crontab -e) :

*/5  *    * * *  PYTHONPATH=/usr/bin/python3 /usr/bin/python3 /home/louis/backup-server/main.py >> /var/log/MYbackup.log 2>&1

But when the cron start the following is logged :

Traceback (most recent call last):
  File "/home/louis/backup-server/main.py", line 7, in <module>
    import config.config as config
  File "/home/louis/python_helpers/config/config.py", line 2, in <module>
    from dotenv import load_dotenv
ModuleNotFoundError: No module named 'dotenv'

however if I run sudo python3 /home/louis/backup-server/main.py the script is correctly executed

I did run sudo pip install python-dotenv

Content of scripts :

# /home/louis/backup-server/main.py
# permissions : -rwxr-xr-x
import os
import requests
import json
import datetime
import sys
sys.path.insert(0, '/home/louis/python_helpers')
import config.config as config
import mail
import utils

def main():
    # some code

if __name__ == "__main__":
    main()

--

# /home/louis/python_helpers/config/config.py
# permissions : -rwxr-xr-x 
import os
from dotenv import load_dotenv
dotenv_path = os.path.join(os.path.dirname(__file__), '.env')
load_dotenv(dotenv_path)
# some config var

I do have an __init__.py file in /home/louis/python_helpers/config, let me know if for any other information I should add.

What bug me the most is that the scripts run just fine if started manually but not as cron.

Edit : I was unsure whether this question belongs here or on stackoverflow, so please tell me if I should move it (even though I don't know how beside creating a new question)

Solution 1:

Well the issue was pretty dumb, I did run pip install python-dotenv and sudo pip install python-dotenv (the script need root permission to access some folder) but I didn't do sudo -H pip install python-dotenv.

After running this command, the cron execute just fine.