message: Fix python2 str() in visualization
diff: @@ -1089,11 +1089,11 @@ class NVD3TimeSeriesViz(NVD3Viz):
  if df[name].dtype.kind not in 'biufc':
  continue
  if isinstance(name, list):
  - series_title = [str(title) for title in name]
  + series_title = [text_type(title) for title in name]
  elif isinstance(name, tuple):
  - series_title = tuple(str(title) for title in name)
  + series_title = tuple(text_type(title) for title in name)
  else:
  - series_title = str(name)
  + series_title = text_type(name)
  if (
  isinstance(series_title, (list, tuple)) and
  len(series_title) > 1 and
  