Warnings generated by test_matrix_operation.py

[cclauss]

Python/matrix/tests/test_matrix_operation.py mentions @pytest.mark.mat_ops numerous times which is generating a lot of warnings every time Travis CI does a build. @StephenGemin, @WilliamHYZhang can you please investigate how to fix the code to suppress these warnings?

[WilliamHYZhang]

Most likely it is due @pytest.mark.mat_ops being an invalid marker, can we remove @cclauss?

[cclauss]

Please give that a try.