I run isbn.py and it shows this error
```
python pwb.py isbn.py -to13 -file:up.txt
Retrieving 50 pages from wikipedia:fa.
Traceback (most recent call last):
File "pwb.py", line 248, in <module>
if not main():
File "pwb.py", line 242, in main
run_python_file(filename, [filename] + args, argvu, file_package)
File "pwb.py", line 120, in run_python_file
main_mod.__dict__)
File "./scripts/isbn.py", line 1659, in <module>
main()
File "./scripts/isbn.py", line 1652, in main
bot.run()
File "./scripts/isbn.py", line 1521, in run
self.treat(page)
File "./scripts/isbn.py", line 1496, in treat
new_text = self.isbnR.sub(_isbn10toIsbn13, new_text)
File "./scripts/isbn.py", line 1458, in _isbn10toIsbn13
i13 = getIsbn(isbn).toISBN13()
AttributeError: 'ISBN13' object has no attribute 'toISBN13'
<type 'exceptions.AttributeError'>
CRITICAL: Closing network session.
```