Hi @FrancescoDeLuca,
It can be related to Ladybug[+]. I think “legend.py” file is missing on your machine.
Try to follow this discussion how to solve it: https://discourse.ladybug.tools/t/problems-with-honeybeeplus-component/6779/5
The installation of Ladybug[+] consist in both .ghuser files into the UserObjects and python library in McNeel folder.
Regards,
Antonello