Update print_ids.py to Python3 (#357)

Author: R-Fehler

lanelet2_python/scripts/print_ids.py

@@ -21,7 +21,7 @@ def print_layer(layer, layerName):
 layers = {"Points": map.pointLayer, "Line Strings": map.lineStringLayer, "Polygons": map.polygonLayer,
           "Lanelets": map.laneletLayer, "Areas": map.areaLayer, "Regulatory Elements": map.regulatoryElementLayer}
 
-for layer_name, layer in layers.iteritems():
+for layer_name, layer in layers.items():
     if not args.has_id:
         print_layer(layer, layer_name)
     else: