As numpy is Python 3 only, these import statements are now unnecessary
and don't alter runtime behavior.

[ci skip]

* Deprecation: numpy.testing.rand

Otherwise the deprecation message is not that helpful as I have to dig
through the source to find out since when and whether conditional import
is necessary in my code. I may not have numpy on my dev machine (this
message was on CI). So it's one extra step for the consumer.

That's also for you, you have more chance of having consumer update
their code when they have more informations in the deprecation message,
so you can drop old code faster !

At least kudo to Charles Harris for including a comments just above,
that prevented me from having to git blame and go spelunking for knowing
which versions were or not affected.

This also means we can now test that our test is actually able to detect the type of failure we expect

Trying to give myself some tools to debug the failure at https://github.com/numpy/numpy/pull/10882/files#r180813166

The following modules have been moved or renamed and should not be
imported. This adds shim modules for the old names that issue a
DeprecationWarning on import.

* numpy/core/umath_tests.py
* numpy/testing/decorators.py
* numpy/testing/noseclasses.py
* numpy/testing/nosetester.py
* numpy/testing/utils.py

Closes #10845.

The warning type is the second, not the first, argument.

Downstream projects were importing directly from the testing modules
rather than from testing. Discourage this.

This is to prepare for the switch to pytest.

* Rename `numpy/testing/nose_tools` to `numpy/testing/_private`.
* Redirect imports as needed.
* Copy `_testutils.py` from scipy to `numpy/testing/_private`.
* Rename `_testutils.py` to `_pytester.py` and remove unneeded bits.