The test suite is installed as a sub-package, so the test data must also be installed along with it. The `__file__` attribute can be missing when importing a zipped package, so we load test files with `pkg_resources.resource_filename()`.
The test suite is installed as a sub-package, so the test data must also be installed along with it. The `__file__` attribute can be missing when importing a zipped package, so we load test files with `pkg_resources.resource_filename()`.