file doesn't exist

[Larz60+]

I always obtain the message 'file doesn't exist'.

Always show the entire error traceback, verbatim

I am not sure why, because the files I use are in the same directory as
the python files

The current working directory may not be the same as the src directory, to assure this is the case, add the following statement as the first line executed:

# add import
import os

#add as first line executed (in front of line 6)
os.chdir(os.path.abspath(os.path.dirname(__file__)))