old_contents: try:
      import readline
  except ImportError:
      print("Module readline not available.")
  else:
      import rlcompleter
      readline.parse_and_bind("tab: complete")
  
new_contents: # File:   pythonrc.py
  # Author: Shoichi Aizawa <shoichiaizawa@gmail.com>
  # Source: https://github.com/shoichiaizawa/dotfiles/tree/master/pythonrc.py
  
  try:
      import readline
  except ImportError:
      print("Module readline not available.")
  else:
      import rlcompleter
      readline.parse_and_bind("tab: complete")
  
subject: add header descriptions