This indeed looks exactly the same as the error I encounter. But I’m confused about the solution. What should I do? Or am I to understand that the addition " is_file()" has to be added tot the Pirinman5 code?
As I do not own a pironman5, rpi5 nor usb-serial, I cannot help any more than I’ve referenced in the previously posted links. I just happen to recall this issue being discussed on another forum that I follow
I’d suggest reposting your question in one of those mentioned forums. Either rpi5 (where a bookworm level solution was proposed) or adafruit, (where an adafruit solution was created)
Although not really a Sunfounder, nor pironman5 issue, Sunfounder may also be able to assist. They are really helpful!
Of course, if Sunfounder send me a free one, then I can help out more 
@Spf650
Thanks, you have found the cause of the issue, so as far as I’m concerned you have earned your Pironman
@Sunfounder Moderator
So the cause of the problem is clear now. Can you advise me how to solve this? I’ve updated the RPi completely, but the issue remains. Apearently the Blinka library in Bookworm is not updated yet.
You are most welcome. Sorry that I could not help any further.