BUG: Fix matrix PendingDeprecationWarning suppression for pytest 3.8+.

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.

7 files changed, 7 insertions, 50 deletions

diff --git a/numpy/matrixlib/tests/test_defmatrix.py b/numpy/matrixlib/tests/test_defmatrix.py
index 272cd8d52..4cff5ee9b 100644
--- a/numpy/matrixlib/tests/test_defmatrix.py
+++ b/numpy/matrixlib/tests/test_defmatrix.py
@@ -1,12 +1,6 @@
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
+import pytest
 
 try:
     # Accessing collections abstract classes from collections
diff --git a/numpy/matrixlib/tests/test_interaction.py b/numpy/matrixlib/tests/test_interaction.py
index fb4d8f98c..088ae3c6a 100644
--- a/numpy/matrixlib/tests/test_interaction.py
+++ b/numpy/matrixlib/tests/test_interaction.py
@@ -4,13 +4,7 @@ Note that tests with MaskedArray and linalg are done in separate files.
 """
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
+import pytest
 
 import textwrap
 import warnings
diff --git a/numpy/matrixlib/tests/test_masked_matrix.py b/numpy/matrixlib/tests/test_masked_matrix.py
index adc2e5419..5ed8044aa 100644
--- a/numpy/matrixlib/tests/test_masked_matrix.py
+++ b/numpy/matrixlib/tests/test_masked_matrix.py
@@ -1,14 +1,7 @@
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
-
 import pickle
+import pytest
 
 import numpy as np
 from numpy.ma.testutils import (assert_, assert_equal, assert_raises,
diff --git a/numpy/matrixlib/tests/test_matrix_linalg.py b/numpy/matrixlib/tests/test_matrix_linalg.py
index 85c7693b4..8d31ec5b0 100644
--- a/numpy/matrixlib/tests/test_matrix_linalg.py
+++ b/numpy/matrixlib/tests/test_matrix_linalg.py
@@ -1,13 +1,7 @@
 """ Test functions for linalg module using the matrix class."""
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
+import pytest
 
 import numpy as np
 
diff --git a/numpy/matrixlib/tests/test_multiarray.py b/numpy/matrixlib/tests/test_multiarray.py
index 2f04b49d6..8de0a7c6a 100644
--- a/numpy/matrixlib/tests/test_multiarray.py
+++ b/numpy/matrixlib/tests/test_multiarray.py
@@ -1,12 +1,6 @@
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
+import pytest
 
 import numpy as np
 from numpy.testing import assert_, assert_equal, assert_array_equal
diff --git a/numpy/matrixlib/tests/test_numeric.py b/numpy/matrixlib/tests/test_numeric.py
index cfdada126..e9f44e747 100644
--- a/numpy/matrixlib/tests/test_numeric.py
+++ b/numpy/matrixlib/tests/test_numeric.py
@@ -1,12 +1,6 @@
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
+import pytest
 
 import numpy as np
 from numpy.testing import assert_equal
diff --git a/numpy/matrixlib/tests/test_regression.py b/numpy/matrixlib/tests/test_regression.py
index 439704ccf..88654c76a 100644
--- a/numpy/matrixlib/tests/test_regression.py
+++ b/numpy/matrixlib/tests/test_regression.py
@@ -1,12 +1,6 @@
 from __future__ import division, absolute_import, print_function
 
-# As we are testing matrices, we ignore its PendingDeprecationWarnings
-try:
-    import pytest
-    pytestmark = pytest.mark.filterwarnings(
-        'ignore:the matrix subclass is not:PendingDeprecationWarning')
-except ImportError:
-    pass
+import pytest
 
 import numpy as np
 from numpy.testing import assert_, assert_equal, assert_raises