Unicodefehler bei der 404 Seite

Traceback (most recent call last):
  File "./server.py", line 38, in sched_wrapper
    func(*args, **kargs)
  File "./server.py", line 225, in dump_error_page
    f.write(text)
UnicodeEncodeError: 'ascii' codec can't encode character '\xfc' in position 3277: ordinal not in range(128)