Thanks to Berker Peksag and Tim Graham for the review and suggestions.

Thanks jwmayfield, serg.partizan, and Wojciech Banaś for work on the patch.

Changed the BaseEmailBackend to allow usage as context manager to open
and close connections.

Thanks Piotr Kasprzyk for help with the patch.

This is quite important otherwise we don't close our connections to the
SMTP server.

Changed console and filebackend to use msg.as_bytes to output the data as it would get send via smtp.

This is to provide a consistent interface (namely bytes) for the smtp
backend which after all sends bytes over the wire; encoding with as_string
yields different results since mails as unicode are not really specified.

as_string stays for backwardscompatibilty mostly and some debug outputs.
But keep in mind that the output doesn't match as_bytes!

Refs #21271.

Thanks Tobias McNulty and Tim Graham for discussions and code review.
Thanks Andre Cruz the suggestion and initial patch.

* Removed trailing whitespace.
* Added newline to EOF if missing.
* Removed blank lines at EOF.
* Removed some stray tabs.

Thanks joseph at vertstudios.com for the suggestion.

Thanks simonb for the report, Claude Paroz and Susan Tan for their work
on a fix.

Thanks Michael Farrell for the report and his work on the fix.

Thanks simonb for the report, Claude Paroz and Susan Tan for their work
on a fix.

Thanks Michael Farrell for the report and his work on the fix.

Thanks dj.facebook at gmail.com for the report and initial patch
and Areski Belaid and senko for improvements.

Gives much nicer errors when it fails.