/usr/lib/python2.7/dist-packages/sage/matrix/ is in sagemath-common 8.1-7ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python2.7/dist-packages/sage/matrix/__init__.py
/usr/lib/python2.7/dist-packages/sage/matrix/action.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/all.py
/usr/lib/python2.7/dist-packages/sage/matrix/benchmark.py
/usr/lib/python2.7/dist-packages/sage/matrix/berlekamp_massey.py
/usr/lib/python2.7/dist-packages/sage/matrix/compute_J_ideal.py
/usr/lib/python2.7/dist-packages/sage/matrix/docs.py
/usr/lib/python2.7/dist-packages/sage/matrix/matrix.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix0.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix1.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix2.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_complex_ball_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_complex_double_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_cyclo_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_domain_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_domain_sparse.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_double_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_generic_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_generic_sparse.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_gf2e_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_gfpn_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_integer_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_integer_dense_hnf.py
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_integer_dense_saturation.py
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_integer_sparse.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_misc.py
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_mod2_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_modn_dense_double.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_modn_dense_float.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_modn_dense_template.pxi
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_modn_dense_template_header.pxi
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_modn_sparse.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_mpolynomial_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_polynomial_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_rational_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_rational_sparse.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_real_double_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_space.py
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_sparse.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_symbolic_dense.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/matrix_window.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/operation_table.py
/usr/lib/python2.7/dist-packages/sage/matrix/special.py
/usr/lib/python2.7/dist-packages/sage/matrix/symplectic_basis.py
/usr/lib/python2.7/dist-packages/sage/matrix/template.pxd
/usr/lib/python2.7/dist-packages/sage/matrix/tests.py