[Zope] Base64 - Encoding/Decoding without external method

[Andrea Lombardoni]

Hello.

I would like to decode/encode data in base64 without resorting 
to an external Python method.

Every function that I tried to use in a Python 
script, such as mimetools.[encode|decode], 
binascii.[a2b_base64|b2a_base64], base64.[b64encode|b64decode] returns an
error:

Error Type: Unauthorized
Error Value: You are not allowed to access encode in this context

Does anyone know a way to do this?