Dear contributors, We'd like to notify your that we have just finished a transition of our testing environment from `nose` to `pytest` (see https://github.com/scikit-image/scikit-image/pull/2468 for the details). We kindly ask you to revisit your open Pull Requests on GitHub, perform a rebase onto `master` branch of `scikit-image/scikit-image` repo (see http://scikit-image.org/docs/dev/contribute.html#divergence-between-upstream...), and rewrite your tests using `pytest` wherever is needed. Usage of the functions from `numpy.testing` in addition to `pytest` ones is allowed, but, please, notice that some of them (such as `assert_raises`) rely on `nose` under the hood, and, therefore, should not be used. Sorry for the inconvenience. Looking forward to seeing your contributions updated and merged. Regards, Egor, scikit-image core team