Include regression tests in PyPI tarball

[kmosiejczuk]

In OpenBSD, we like to have the regression tests available in the tarball so we can easily do regression tests when updating ports.

[K0lb3]

As you've seen, the current tests are quite minimal and have to be extended.
When this is done the size of the binary test files will necessarily increase.
That's why I'm not really a fan of including them in the build package.

I could change the test script a bit,
so that it downloads the test files on demand.
By doing so the build package will stay small while the tests can still be executed without much trouble.