title: Python Flask UnsupportedOperation: not writable
body: <p>When I run the following code, I get the error message: "UnsupportedOperation: not writable":</p>
  
  <pre><code>from flask import Flask
  
  app_flask = Flask(__name__)
  
  @app_flask.route('/')
  def hello_method():
      return "Hello, main page!"
  
  if __name__ == '__main__':
      app_flask.run()
  </code></pre>
  
  <p>Can anyone offer some guidance? I know there's another question like this one, but the answers were not helpful at all. Here's the rest of the error message:</p>
  
  <pre><code>Traceback (most recent call last):
  
    File "&lt;ipython-input-13-a122d150300b&gt;", line 20, in &lt;module&gt;
      app_flask.run()
  
    File "C:\anaconda3\lib\site-packages\flask\app.py", line 938, in run
      cli.show_server_banner(self.env, self.debug, self.name, False)
  
    File "C:\anaconda3\lib\site-packages\flask\cli.py", line 629, in show_server_banner
      click.echo(message)
  
    File "C:\anaconda3\lib\site-packages\click\utils.py", line 259, in echo
      file.write(message)
  
  UnsupportedOperation: not writable
  </code></pre>