Cookiecutter-django: Unconditionally connect to database from DATABASE_URL env when opting for Docker

[webyneter]

E.g. in config.settings.base:

DATABASES = {
    'default': env.db('DATABASE_URL'),
}

[wandering-tales]

I currently use Docker for local development, but removing the default value Travic CI builds fail.

[browniebroke]

Yes, the Travis config isn't suitable for Docker currently. See #2100

[wandering-tales]

Great! Good to know the issue has been reported.

I tried to apply the changes proposed in #1950. But unfortunately that was not enough. My current workaround was to provide the following default value for the DATABASE_URL environment variable, not explicitly set in non-Docker deployments:

DATABASES = {
    'default': env.db('DATABASE_URL', default='postgres:///{{cookiecutter.project_slug}}'),
}

I wonder why that default has been removed in 6c26d39f65a66429ae1ec9a00d9676f29c408c45.