Custom migrations that create a postgres role run against the production database during tests (postgres 9.6)

[Simon Tomlinson]

Creating a custom migration that uses migrations.RunSQL to create a new postgres role and then running tests using python manage.py test creates the role in the real postgres server (when running postgres 9.6).

This doesn't happen with other custom sql, such as creating a type, which I found very odd.

Attached is a django project configured to connect to a postgres database running on localhost:5432, with a "postgres" user with no password and a postgres database. It contains an app called "app" with a single migration that executes CREATE ROLE test_role.

Run python manage.py test and then inspect the database to reproduce. The role test_role should exist (list it with \du in psql).
Alternatively, run python manage.py test twice. It will crash the second time because the role already exists from the first run.

[Simon Tomlinson]

Django project exhibiting the problem

[Simon Tomlinson]

I just realized that roles aren't database specific. Of course this happens.