Python 2 fix (keyword parameter not allowed after *args)

Author: jonmmease

plotly/basedatatypes.py

@@ -3145,7 +3145,7 @@ def _dispatch_change_callbacks(self, changed_paths):
                 for callback in callbacks:
                     callback(self, *callback_args)
 
-    def on_change(self, callback, *args, append=False):
+    def on_change(self, callback, *args, **kwargs):
         """
         Register callback function to be called when certain properties or
         subproperties of this object are modified.
@@ -3215,6 +3215,10 @@ def on_change(self, callback, *args, append=False):
             raise ValueError(
                 'Invalid property specification(s): %s' % invalid_args)
 
+        # Process append option
+        # ---------------------
+        append = kwargs.get('append', False)
+
         # Normalize args to path tuples
         # -----------------------------
         arg_tuples = tuple([BaseFigure._str_to_dict_path(a) for a in args])