raw_data_manager (default for EmailPolicy, EmailMessage)
does correct wrapping of 'text' parts as long as the message contains
characters outside of 7bit US-ASCII set: base64 or qp
Content-Transfer-Encoding is applied if the lines would be too long
without it. It did not, however, do this for ascii-only text,
which could result in lines that were longer than
policy.max_line_length or even the rfc 998 maximum.
This changeset fixes the heuristic so that if lines are longer than
policy.max_line_length, it will always apply a
content-transfer-encoding so that the lines are wrapped correctly.
This adds EmailMessage and, MIMEPart subclasses of Message
with new API methods, and a ContentManager class used by
the new methods. Also a new policy setting, content_manager.
Patch was reviewed by Stephen J. Turnbull and Serhiy Storchaka,
and reflects their feedback.
I will ideally add some examples of using the new API to the
documentation before the final release.
