Sites migration fails when DATABASES['default'] = {}

[Thomas Recouvreux]

On Django 1.7.4 the management command migrate --database=xxx fails when DATABASES['default'] = {} with django.core.exceptions.ImproperlyConfigured: settings.DATABASES is improperly configured. Please supply the ENGINE value. Check settings documentation for more details..
On Django 1.7.3 it works fine.
More details can be found on https://code.djangoproject.com/ticket/24298.

To reproduce the problem:

1. Create a new project
2. Edit the settings.py this way:

DATABASES = {
    'default': {},
    'mysite': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db_mysite.sqlite3'),
    }
}

3. Run python manage.py migrate --database=mysite

Problem:
It seems Django tries to access the default connection.

I am attaching an output log of the command.
Here is a sample project to reproduce the behaviour: ​​https://github.com/trecouvr/test_dj_migrate_174.

[Tim Graham]

This seems to be a duplicate of #24298 which was fixed (did you try this on the stable/1.7.x branch?). Markus asked you to open a new issue for create_default_site() not propagating the using parameter. Did you misunderstand him or am I misunderstanding you?

[Thomas Recouvreux]

I am not sure if I misunderstood him or not, but I get the error reported on this ticket with branch stable/1.7.x and this is not exactly the same as mentioned in #24298. This looks like the same as #24298 but the root cause is not the same (The root cause of #24298 is the post_migrate call related to the 'auth' application whereas here the error is related to the 'sites' application).

[Tim Graham]

Oh, I see, will look at this.

[Tim Graham]

​PR (not sure about tests at the moment)

[Tim Graham]

Tests added.

[Tim Graham <timograham@…>]

In e8cf4f8abec87b9da6ed8e5c8cf833af9b27f4dd:

Fixed #24332 -- Fixed contrib.sites create_default_site() when 'default' DATABASES is empty.

[Tim Graham <timograham@…>]

In 1b93b0977d2fa7d3cca2fb64168655582e7a88f9:

[1.7.x] Fixed #24332 -- Fixed contrib.sites create_default_site() when 'default' DATABASES is empty.

Backport of e8cf4f8abec87b9da6ed8e5c8cf833af9b27f4dd from master

[Tim Graham <timograham@…>]

In 4c948c7c9d8b8bb4a36f703a6e96de5914740b0f:

[1.8.x] Fixed #24332 -- Fixed contrib.sites create_default_site() when 'default' DATABASES is empty.

Backport of e8cf4f8abec87b9da6ed8e5c8cf833af9b27f4dd from master