Update get_payload to decode the Content-Transfer-Encoding header

[noahbass]

Addresses some issues in #2.

This will decode the message payload if it's in base64 or quoted-printable as the Content-Transfer-Encoding header.

So with these changes, this message with a quoted-printable Content-Transfer-Encoding header:

Hello world, =0A=0AIf Lorem ipsum dolor sit amet, consectetur=
adipiscing elit. Donec vel ex egestas ante scelerisque vulputate eget et me=
us. =0A=0A In non sollicitudin nulla,=
accumsan vehicula velit=

Will now be output as this:

Hello world, Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec vel ex egestas ante scelerisque vulputate eget et metus. In non sollicitudin nulla, accumsan vehicula velit.

See get_payload documentation for details on using decode=True.

[isiah-lloyd]

I don't know how many emails it would affect but it seems like setting decode to true will cause get_payload() to return None if the email is a multipart message. Should we check the content type before that and then set decode to true only if the message is not multipart?

[noahbass]

Maybe this block would work better? (Untested)

msg_body = ""
for part in msg.walk():
    if part.get_content_maintype() == 'multipart':
        continue
    if part.get_content_type() == 'text/plain':
        msg_body = part.get_payload(decode=True)

part can be a multipart, so if it is then just skip over it?

[noahbass]

Well, actually I've thought about it and since the loop walks through each part in a message (which could be a multipart message):

msg_body = ""
for part in msg.walk():
    if part.get_content_type() == 'text/plain':
        msg_body = part.get_payload(decode=True)
        break

When it reaches get_payload(decode=True), part will never have content-type multipart b/c the content-type will always be text/plain, so the get_payload will always work.

[isiah-lloyd]

I think that looks good.

EDIT: Actually what about an else clause so that get_payload() is called with decode false so that a multipart message is still posted?