Migrate to Pytest

[rth]

Closes #327

nose is not longer maintained and most popular packages in the scientific python community have migrated to pytest. The existing tests will run without modifications with pytest, but it will make easier,

• cleaning up temporary files (Do not leave files after running unit tests #447)
• running some tests without actually connecting to the server without using mock responses, as it e.g. done in the openml loaded in scikit-learn.

[rth]

CI is green.

What do you think about this @mfeurer @janvanrijn ?

[mfeurer]

Looks good to me. Could you please explain why use you replaced python setup.py develop by pip install -e '.[test]`` and what the argument '.[test]'` does?

[rth]

So, pip install is now the recommended way to install packages (even local packages) as compared to python setup.py install (see https://packaging.python.org/tutorials/installing-packages/#installing-from-a-local-src-tree).

pip install .  # dot important at the end

installs the local package.

To get the behavior of develop, it's necessary to add the -e flag.

And to install extra dependencies, one would do,

pip install openml[test]

which installs extra "test" dependencies specified in the setup.py. So the sum of that in this case is,

pip install -e .[test]

with some parenthesis as I wasn't sure how bash would handle it.

[mfeurer]

Thanks a lot for explaining this. I just talked to @janvanrijn and he's okay with merging this. Thanks a lot!

[rth]

Thanks for the review @mfeurer !