"AttributeError: 'NoneType' object has no attribute 'cancel'"
I think you found another way to hit this bug: https://bugs.launchpad.net/ubuntu/+source/calibre/+bug/1898904
"AttributeError: 'NoneType' object has no attribute 'cancel'"
I think you found another way to hit this bug: https:/ /bugs.launchpad .net/ubuntu/ +source/ calibre/ +bug/1898904