Tkinter md5 problem

[Dagur Páll Ammendrup]

Hi!

In the Introduction to Tkinter I found this method to detect if the 
contents in a Text widget have changed:

---------------------------------------------------
import md5
     def getsignature(contents):
         return md5.md5(contents).digest()

     text.insert(END, contents) # original contents
     signature = getsignature(contents)

     ...

     contents = text.get(1.0, END)
     if signature != getsignature(contents):
         print "contents have changed!"

---------------------------------------------------

This does work, but only if you're using ASCII, otherwise you get a 
UnicodeError

UnicodeError: ASCII encoding error: ordinal not in range(128)

So what can I do?
Thanks in advance!

-Dagur