Installing pygal under Ubuntu 18.04

[ybeco]

When I rename "pygal.py" in "foobarbaz.py" the error message don't come back
But the graph does not appear and I have this message:

Output:
Python 3.7.0b3 (default, Mar 30 2018, 04:35:22) 
[GCC 7.3.0] on linux
Type "copyright", "credits" or "license()" for more information.
>>> 
 RESTART: /media/yonnel/SSD-1T/yonnel/Dropbox/00- DIY/11- Python/02- Essais/Pygal/foobarbaz.py 
>>> 

I looked for what he meant by "RESTART:", but I did not find it...