Typical behaviour in the shell is to treat existing environment variables containing nothing the same as a if the env variable is not defined. `trytond.config` does not behave like this: ``` $ env -u DB_NAME -u TRYTOND_CONFIG -u TRYTOND_DATABASE_URI python -m unittest discover -vvvvv -s modules/party/tests/ … Ran 51 tests in 16.400s OK $ TRYTOND_DATABASE_URI= env -u TRYTOND_CONFIG -u DB_NAME python -m unittest discover -vvvvv -s modules/party/tests/ … ModuleNotFoundError: No module named 'trytond.backend.' … ``` trytond-6.8.0 **Expected behaviour**: both commands work the same way This is caused by https://foss.heptapod.net/tryton/tryton/-/blob/trytond-6.8.2/trytond/trytond/config.py#L60-61