input: Write a function to delete a specified directory and all its content, and print a message upon successful deletion.
  assert delete_directory('test_dir')==None
  assert delete_directory('non_existent_dir')==None
output: import shutil
  import os
  
  def delete_directory(directory):
      try:
          shutil.rmtree(directory)
          print(f"Directory '{directory}' and all its contents have been successfully deleted.")
      except FileNotFoundError:
          print(f"Directory '{directory}' does not exist.")