[Zope] Base64 - Encoding/Decoding without external method

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?