Exception sending EmailMessage with body=None

[Alex Schokking]

This had been working fine on 1.9 but when we upgraded to 1.11 instantly started hitting an exception when django tries to call splitlines on the None body without checking if there's a value there to split on.

 File "/usr/local/lib/python2.7/dist-packages/django/core/mail/message.py", line 348, in send
    return self.get_connection(fail_silently).send_messages([self])
  File "/usr/local/lib/python2.7/dist-packages/django/core/mail/backends/smtp.py", line 111, in send_messages
    sent = self._send(message)
  File "/usr/local/lib/python2.7/dist-packages/django/core/mail/backends/smtp.py", line 125, in _send
    message = email_message.message()
  File "/usr/local/lib/python2.7/dist-packages/django/core/mail/message.py", line 307, in message
    msg = SafeMIMEText(self.body, self.content_subtype, encoding)
  File "/usr/local/lib/python2.7/dist-packages/django/core/mail/message.py", line 214, in __init__
    MIMEText.__init__(self, _text, _subtype=_subtype, _charset=_charset)
  File "/usr/lib/python2.7/email/mime/text.py", line 30, in __init__
    self.set_payload(_text, _charset)
  File "/usr/local/lib/python2.7/dist-packages/django/core/mail/message.py", line 224, in set_payload
    for l in payload.splitlines()
AttributeError: 'NoneType' object has no attribute 'splitlines'

We've hacked around it by passing in an empty string instead but would probably be more elegant for this has_long_lines logic to check if there's a value instead.

For context we're not passing in a body because we're attaching the plaintext and html versions of the email as a SafeMIMEMultipart attachment.