b64encode and unicode problem

[Gabriel Rossetti]

Hello everyone,

I am trying to encode a string using b4encode and I get the following 
error :

 >>> b64encode(u"Salut Pierre, comment ça va?")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/base64.py", line 53, in b64encode
    encoded = binascii.b2a_base64(s)[:-1]
UnicodeEncodeError: 'ascii' codec can't encode character u'\xe7' in 
position 22: ordinal not in range(128)

If I remove the "u" infront of the string, it works. The problem is that 
I in my program, the string is given to me un unicode/utf-8. I tried 
several things, but I still get it, How can I get it to work, anybody 
have any idea?

Thanks,
Gabriel