- When tax is known but zero, line_tax should return Decimal(0).
- When tax is not known, line_tax should return None.

Fixes #2395.

* Add datetime attribute to ProductAttributeValue as asked for in issue #2389

Used widget DateTimePickerInput from oscar.forms.widgets

* Fix migration catalogue 0012 (was error with python3)

* Add tests for ProductAttributeValue

In Python 2, adding None to the basket total worked, but in Python 3 this raises a TypeError. This fixes the handling of totals to distinguish between a zero price and a non-existent price.

* fix bug in grouped_voucher_discounts

* add test for grouped_voucher_discounts

* remove 3.6.1 syntax

* improve test

- Refactor clean methods to return all validation errors, rather than just the first one we found.
- Fix clean method type errors in Python 3
- Add tests for the clean methods for all benefit types.

Fixes #2277.

- If start_datetime is null, then the offer has no start date.
- If end_datetime is null, then the offer never expires.

Use the ActiveOfferManager in Applicator.get_site_offers instead of
reimplementing the same logic there.

Fixes #2344.

Also remove some Django 1.6 compatibility code.

Fixes #2176.

Django 1.9 introduced the AUTH_PASSWORD_VALIDATORS setting which allows for
more flexible password validation. Switch to using that when it is available,
with a fallback to Oscar's previous behaviour in Django 1.8 or when this
setting is empty.

This was removed from the parent class way back in Django 1.4, and was
not being used at all here. It existed only for backwards compatibility.

Fixes #2168.

Now after ConditionalOffer deleted will be deleted related Benefits and Conditions models (through post_delete signal) if they are no longer used by other offers (with exception of custom benefits/conditions). Plus some small changes related to PEP8 and typos.

It seems that migrations are unicode in Django 1.11

Since Django 1.11 dicts should be passed to template rendering functions

The initial check if the voucher is available was done before creating
the order. This change adds a validation step during the order creation
within an atomic() block.

See #2101

Most real-world instances will use postgresql instead of sqlite so it's
better to use postgres for the tests. This also allows us to easily add
tests for concurrency issues which is not supported by sqlite

The pk kwarg on views is a string type. The message format string was expecting a numeric value. This updates that format string to expect a string value, which will always display correctly.

As in `test_model.py` -> `test_models.py`

The idea of splitting integration from unittests is good in theory
but leads to a lot of mental overhead. Besides whenever a tests
interacts with a database it isn't a unittest anyway.

Better to use filenames which are commonly used in the python word then
custom ones.

Latter one is deprecated