/usr/include/CGAL/Partition_2/ is in libcgal-dev 4.2-5ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/CGAL/Partition_2/Circulator_pair.h
/usr/include/CGAL/Partition_2/Indirect_edge_compare.h
/usr/include/CGAL/Partition_2/Indirect_less_xy_2.h
/usr/include/CGAL/Partition_2/Indirect_not_less_yx_2.h
/usr/include/CGAL/Partition_2/Iterator_list.h
/usr/include/CGAL/Partition_2/Matrix.h
/usr/include/CGAL/Partition_2/Partition_opt_cvx_diagonal_list.h
/usr/include/CGAL/Partition_2/Partition_opt_cvx_edge.h
/usr/include/CGAL/Partition_2/Partition_opt_cvx_vertex.h
/usr/include/CGAL/Partition_2/Partition_traits_2_base.h
/usr/include/CGAL/Partition_2/Partition_vertex_map.h
/usr/include/CGAL/Partition_2/Partitioned_polygon_2.h
/usr/include/CGAL/Partition_2/Point_pair_less_xy_2.h
/usr/include/CGAL/Partition_2/Rotation_tree_2.h
/usr/include/CGAL/Partition_2/Rotation_tree_2_impl.h
/usr/include/CGAL/Partition_2/Rotation_tree_node_2.h
/usr/include/CGAL/Partition_2/Segment_less_yx_2.h
/usr/include/CGAL/Partition_2/Triangulation_indirect_traits_2.h
/usr/include/CGAL/Partition_2/Turn_reverser.h
/usr/include/CGAL/Partition_2/Vertex_visibility_graph_2.h
/usr/include/CGAL/Partition_2/Vertex_visibility_graph_2_impl.h
/usr/include/CGAL/Partition_2/is_degenerate_polygon_2.h
/usr/include/CGAL/Partition_2/partition_approx_convex_2.h
/usr/include/CGAL/Partition_2/partition_assertions.h
/usr/include/CGAL/Partition_2/partition_greene_approx_convex_2.h
/usr/include/CGAL/Partition_2/partition_optimal_convex_2.h
/usr/include/CGAL/Partition_2/partition_y_monotone_2.h