old_contents: try:
      from tkinter import Tk, Entry, Label, Button, Scrollbar, Checkbutton,\
                          IntVar, Text, WORD, CURRENT, END, N, S, E, W
  except ImportError:
      from Tkinter import Tk, Entry, Label, Button, Scrollbar, Checkbutton,\
                          IntVar, Text, WORD, CURRENT, END, N, S, E, W
  
new_contents: try:
      from tkinter import Tk, Entry, Label, Button, Scrollbar, Checkbutton,\
                          TclError, IntVar, Text, WORD, CURRENT, END, N, S, E, W
  except ImportError:
      from Tkinter import Tk, Entry, Label, Button, Scrollbar, Checkbutton,\
                          TclError, IntVar, Text, WORD, CURRENT, END, N, S, E, W
  
subject: Add import of TclError