Convert the attachments in the email to the appropriate format for
        sending with Connection.send().

def _process_attachments(self, email):
        """
        Convert the attachments in the email to the appropriate format for
        sending with Connection.send().
        """
        for a in email.attachments:
            if isinstance(a, MIMEBase):
                if not a.is_multipart():
                    obj = {
                        'filename': a.get_filename(),
                        'content_type': a.get_content_type(),
                    }
                    if a.get('content-transfer-encoding') == 'base64':
                        obj['content'] = a.get_payload()
                        obj['encoded'] = True
                    else:
                        obj['content'] = a.get_payload(decode=True)
                    yield obj
            else:
                yield {
                    'filename': a[0],
                    'content_type': a[2],
                    'content': a[1],
                }