Unicode error in mobi.py

[8b00001000]

Traceback (most recent call last):
  File "pthcode/alexandria/alexandria", line 492, in <module>
    if __name__ == '__main__': main()
  File "pthcode/alexandria/alexandria", line 490, in main
    upload(filename, config, trackers)
  File "pthcode/alexandria/alexandria", line 438, in upload
    isbn = extract_isbn(filename)
  File "pthcode/alexandria/alexandria", line 408, in extract_isbn
    b = mobi.Book(filename)
  File "~/pthcode/alexandria/mobi.py", line 109, in __init__
    d = f.read(68)
  File "/usr/lib/python3.4/codecs.py", line 319, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode bytes in position 37-38: invalid continuation byte