old_contents: """`main` is the top level module for your Flask application."""
  
  # Import the Flask Framework
  from flask import Flask
  app = Flask(__name__)
  # Note: We don't need to call run() since our application is embedded within
  # the App Engine WSGI application server.
  
  
  @app.route('/')
  def hello():
      """Return a friendly HTTP greeting."""
      return 'Hello World!'
  
  
  @app.errorhandler(404)
  def page_not_found(e):
      """Return a custom 404 error."""
      return 'Sorry, Nothing at this URL.', 404
  
new_contents: """`main` is the top level module for your Flask application."""
  
  # Import the Flask Framework
  from flask import Flask
  app = Flask(__name__)
  # Note: We don't need to call run() since our application is embedded within
  # the App Engine WSGI application server.
  
  
  @app.route('/')
  def hello():
      """Return a friendly HTTP greeting."""
      return 'Hello World!'
  
  
  @app.errorhandler(404)
  def page_not_found(e):
      """Return a custom 404 error."""
      return 'Sorry, Nothing at this URL.', 404
  
  
  @app.errorhandler(500)
  def page_not_found(e):
      """Return a custom 500 error."""
      return 'Sorry, unexpected error: {}'.format(e), 500
  
subject: Add custom 500 error handler so app handler errors aren't supressed