Fix regression from PR 3547 (#3560)

Author: finsberg

python/test/unit/io/test_xdmf_function.py

@@ -245,8 +245,8 @@ def gmsh_tet_model(order):
             model.mesh.setOrder(order)
             gmsh.option.setNumber("General.Terminal", 0)
 
-        msh, _, _ = gmshio.model_to_mesh(model, comm, 0)
-        return msh
+        mesh_data = gmshio.model_to_mesh(model, comm, 0)
+        return mesh_data.mesh
 
     def gmsh_hex_model(order):
         model = gmsh.model()
@@ -281,8 +281,8 @@ def gmsh_hex_model(order):
             model.addPhysicalGroup(3, volume_entities, tag=1)
             model.setPhysicalName(3, 1, "Mesh volume")
 
-        msh, _, _ = gmshio.model_to_mesh(gmsh.model, comm, 0)
-        return msh
+        mesh_data = gmshio.model_to_mesh(gmsh.model, comm, 0)
+        return mesh_data.mesh
 
     # -- Degree 1 mesh (tet)
     msh = gmsh_tet_model(1)