I thought that the Python 2 package set was entirely separate from
the Python 3 one, but this appears to actually be using the main
nose package. The actual code doesn’t use nose at all, and their
`tox.ini` uses unittest, so let’s fix that…
checkInputs used to be added to nativeBuildInputs. Now we have
nativeCheckInputs to do that instead. Doing this treewide change allows
to keep hashes identical to before the introduction of
nativeCheckInputs.