[skip ci] fix SyntaxWarning: 'is not' with a literal. Did you mean '!='?
[skip ci] fix SyntaxWarning: 'is not' with a literal. Did you mean '!='?

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