Parsing email payload in python, converting into a string

I'm trying to make a program that will get the content of an email, my current code is as follows:

def get_message_content(_msg):
    def get_section(msg):
        payload = msg.get_payload()
        if type(payload) is list:
            for part in payload:
                for _content in get_section(part):
                    yield _content
        else:
            content_type = msg.get_content_type()
            if content_type == 'text/plain':
                if msg['Content-Transfer-Encoding'] == 'base64':
                    yield b64decode(payload).decode('utf-8')
                else:
                    yield payload

    return ''.join(content for content in get_section(_msg))

Where _msg is an email object This works fine when the email is encoded in base64 or ASCII, but if the email is encoded in quoted-printable then it doesn't work properly (i get lots of = in my output). I was unable to use quopri.decodestring to decode quoted printable, and cant seem to get msg.get_payload(decode=True) to work either.

How can I resolve this? Thanks