FEM: Fenics mesh: export and marking, fixed flake8 issues
FEM: Fenics mesh: export and marking, fixed flake8 issues

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master