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.
* dosage: 2018.04.08 -> 2.17
I've assumed maintainership of the expression because there was none.
Using `fetchPypi` rather than `fetchFromGithub` because the Github tarballs
don't contain all the metadata necessary for the installation.
* dosage: Use pytestCheckHook rather than py.test
* dosage: Re-add test dependencies
* dosage: Add setuptools_scm build input
* dosage: Add six dependency
