Your 5 year old plugin is not Python 3.8 compatible.
Example:
The urllib2 module has been split across several modules in Python 3 named urllib.request and urllib.error.
Code:
""model.py: This is a QAbstractTableModel that holds a list of Metadata objects created from books in an OPDS feed"""
__author__ = "Steinar Bang"
__copyright__ = "Steinar Bang, 2015"
__credits__ = ["Steinar Bang"]
__license__ = "GPL v3"
import datetime
from PyQt5.Qt import Qt, QAbstractTableModel, QCoreApplication
from calibre.ebooks.metadata.book.base import Metadata
from calibre.gui2 import error_dialog
from calibre.web.feeds import feedparser
import urlparse
import urllib2
import json
import re
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