[Tests] refactor tests

[patrickvonplaten]

This PR separates AWS and Local tests to remove these ugly statements in the script:

        if "/" not in dataset_name:
            logging.info("Skip {} because it is a canonical dataset")
            return

To run a aws test, one should now run the following command:

pytest -s tests/test_dataset_common.py::AWSDatasetTest::test_builder_class_wmt14

The same local test, can be run with:

pytest -s tests/test_dataset_common.py::LocalDatasetTest::test_builder_class_wmt14

[lhoestq]

Nice !

[lhoestq]

is there a problem with black smh ?

[patrickvonplaten]

I don't know whether that's black or isort, but I don't think it's a problem.

It's just that we don't check quality on the datasets folder at the moment - see the .circle_ci folder, but I added ./datasets to the Make style file. So I think it's just that some people upload datasets without formatting them and I correct it :D

[patrickvonplaten]

IMO, we should add ./datasets to the circle ci quality check!