respect -nopopup

examples/api/renumbering.py

 import gmsh
+import sys
+
 gmsh.initialize()
 gmsh.option.setNumber("Mesh.MeshSizeMax", 0.1)
 gmsh.option.setNumber("Mesh.MeshSizeMin", 0.1)
@@ -8,14 +10,17 @@ gmsh.model.occ.addRectangle(0,0,0, 1,1)
 gmsh.model.occ.synchronize()
 
 gmsh.model.mesh.generate()
+if '-nopopup' not in sys.argv:
     gmsh.fltk.run()
 
 old, new = gmsh.model.mesh.computeRenumbering('RCMK')
 gmsh.model.mesh.renumberNodes(old, new)
+if '-nopopup' not in sys.argv:
     gmsh.fltk.run()
 
 old, new = gmsh.model.mesh.computeRenumbering('Hilbert')
 gmsh.model.mesh.renumberNodes(old, new)
+if '-nopopup' not in sys.argv:
     gmsh.fltk.run()
 
 gmsh.finalize()