Multipart message body cannot be read with Python 3

[kiilivi]

Get Multipart Payload keyword seems to fail for email body if the e-mail has an attachment. I get this error:
AttributeError: 'str' object has no attribute 'decode'

I googled for that error, and it seems that the message cannot be decoded in the same way in Python 3.
https://stackoverflow.com/questions/28583565/str-object-has-no-attribute-decode-python-3-error

[4nif]

@lasselindqvist I am facing same error too

[lasselindqvist]

I will happily merge any fixes to this problem.