pytest-iam reads local `.env` files

[azmeuk]

If a .env exists, with flask vars filled such as SERVER_NAME, then the values are read by the Canaille instance, leading it to be incorrectly configured. In the end the unit tests fail.
A solution to this could be to disable .env in Canaille.

[azmeuk]

This is now available with 0.0.12: https://pytest-iam.readthedocs.io/en/latest/configuration.html