Inheriting from object was necessary for Python 2 compatibility to use
new-style classes. In Python 3, this is unnecessary as there are no
old-style classes.

Dropping the object is more idiomatic Python.

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

* Review F401,F841,F842 flake8 errors (unused variables, imports)

* Review comments

* More tests in test_installed_npymath_ini

* Review comments

Pytest < 3.8 ignored warnings issued during test collection, but that
changed in pytest 3.8 and the method NumPy used to suppress the
PendingDeprecationWarning for matrices no longer worked, or rather, was
exposed as not working. The fix here is to suppress the warning in
pytest.ini and pytesttester.py , which should work as long as the tests
are the only places left where NumPy uses matrices.

An alternate fix is to delay the construction of matrices in the tests
until they are actually run, which has the virtue of test localization
but is a bit more complicated.

See https://github.com/pytest-dev/pytest/issues/3945 for discussion.

That function is nose specific and has not worked since `__init__` files
were added to the tests directories.

This is an ugly hack to preserve backwards compatibility for code
that uses matrices. It is needed since both diag and diagonal have
been changed to preserve subtypes otherwise.

Note that a.diagonal() still returns matrices when a is a matrix.

If x is a matrix, np.diag(x) and np.diagonal(x) now return matrices
instead of arrays.  Both of these cause x.diagonal() to be called.
That means they return row vectors (just like x.flatten(), x.ravel(),
x.cumprod(), etc.)

allows passing flags like --pdb to test files
also add call to files where its missing