Use Django's --keepdb with Django 1.8+

[blueyed]

Django 1.8 supports --keepdb [1], and it makes sense to make use of
it. This should probably handle migrations in the context of
transactional_db better, i.e. by re-applying migrations with a flushed
DB.

1: https://docs.djangoproject.com/en/1.8/ref/django-admin/#django-admin-option---keepdb

[blueyed]

Please note that this will change the errors you will see when the test database cannot be created on PostgreSQL, because Django will ignore the error from CREATE DATABASE with --keepdb.

Reported for Django at https://code.djangoproject.com/ticket/25406.

[landscape-bot]

Code quality remained the same when pulling 93fca47 on blueyed:use-keepdb-dj18 into b9eb210 on pytest-dev:master.

[landscape-bot]

Code quality remained the same when pulling a5452b6 on blueyed:use-keepdb-dj18 into d3e03b9 on pytest-dev:master.

[pelme]

This is great! Is this fully backward compatible with our old monkey patching? (I guess it is since all tests passes)

I think we should deprecate --reuse-db and just stick with --keepdb and follow the Django conventions. In some distant future we can just drop our own monkey patches altogether and use Django's builtin support. :)

[blueyed]

I think we should deprecate --reuse-db and just stick with --keepdb

👍

Will you do it?

[pelme]

I'd like to get a new release out and will focus on that for now, but I can give it a shot after that if you or no-one else gets there before me :)

[pelme]

(I have no problem merging this before btw, we can do the deprecation in a separate PR)

[blueyed]

Is this fully backward compatible with our old monkey patching?

The errors are different, because it triggers a bug in Django (#261 (comment)).

Maybe it is better to not mess with it for the next release then?

[agamdua]

This would be a really cool thing to have - I would like to drop pytest in a project I'm on now, but its dependent on the --keepdb flag.

I guess this is conditional on a solution to https://code.djangoproject.com/ticket/25406.. Can I help in any way?

[pelme]

I have merged this now but not deprecated --reuse-db yet.

@agamdua You can already get the same functionality with --reuse-db (and it has been possible for quite some time). This PR is about using the Django implementation for database reuse rather than our own. :)