Minimum supported versions are now Django 2.0, Python 3.5.
This touches a lot of code, to:
* Remove obsolete portability code and workarounds
(six, backports of email parsers, test utils, etc.)
* Use Python 3 syntax (class defs, raise ... from, etc.)
* Correct inheritance for mixin classes
* Fix outdated docs content and links
* Suppress Python 3 "unclosed SSLSocket" ResourceWarnings
that are beyond our control (in integration tests due to boto3,
python-sparkpost)
Tox:
* Add Tox factor for extras (all, none, individual ESP).
For now, only break out ESPs that have specific extra
dependencies (amazon_ses, sparkpost).
* Install most package dependencies (including extras)
through the package itself.
* Use new runtests.py environment vars to limit test tags
when Tox isn't installing all extras.
Travis:
* Rework matrix to request specific TOXENVs directly;
drop tox-travis.
Test runner (runtests.py):
* Centralize RUN_LIVE_TESTS logic in runtests.py
* Add ANYMAIL_ONLY_TEST and ANYMAIL_SKIP_TESTS env vars
(comma-separated lists of tags)
Test implementations:
* Tag all ESP-specific tests with ESP
* Tag live tests with "live"
* Don't import ESP-specific packages at test module level.
(Test discovery imports test modules before tag-based filtering.)
Closes#104
Simplify Postmark tracking webhook code by using new "RecordType"
field introduced with Postmark "modular webhooks". (Rather than
looking for fields that are probably only in certain events.)
Also issue configuration error on inbound url installed as tracking
webhook (and vice versa).
