Tests in examples_test.py fail when run from outside the test dir

[elcorto]

The issue doesn't affect the CI since examples are excluded.

These tests need to be run from within /path/to/mala/test/ because (i) of the usage of relative paths in runpy.run_path() and (ii) since all examples save their artifacts to a relative path, so when run from

/path/to/mala/test/

those will end up there. Also examples expect artifacts which they read, such as "be_model.zip", to be in the dir where the script is executed in. An obvious fix to allow running pytest from anywhere, in particular from the package root dir, is to use absolute paths. Then we pollute this dir with artifacts but can clean that with running /path/to/mala/test/clean.sh in the package root. However, a more clean way would be:

• use absolute paths
• execute tests in a temp dir, using tempfile.TemporaryDirectory or pytest tooling

See e.g. here for a possible way to do it.