Please add a line about ALLOWED_HOSTS requirement in tutorial

[Gert van Dijk]

Summary: Since 1.5 one needs to set the ALLOWED_HOSTS to something sane before Django will serve anything besides an empty HTTP-500 response without any form of error output. Please include that in the tutorial or provide a message to the admin.

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I'm new to Django and followed the tutorials using Django 1.5. After finishing the tutorial I wasn't able to use the simple project with the Poll app without keeping DEBUG = True -- all requests were responded with an "500 Server Error". Changing back to Debug = True generated the regular debug enabled responses. Creating the 404.html and 500.html templates didn't help either.

Even every new empty Django project I started wasn't able to serve other than an empty 500 response, unless I would turn on debug mode again. This totally confused me and it took me quite some time to find the right documentation about it in the ​Deployment Checklist (only development version). As raising the SuspicousOperation Exception isn't logged or reported anywhere running the server in production, I did not have any clue! Moreover, this isn't debug-able for me as a new user as it does not show up with Debug mode on.

This Q&A on StackOverflow illustrates the issue perfectly as well (this saved my day!): ​Django: Setting DEBUG = False causes 500 Error

Suggested solution 1: Add a small note about this in the ​Tutorial part 3 paragraph "Write a 404 (page not found) view" where it's explained about the behaviour of the DEBUG value and 404/500 responses. E.g.: "Changed in Django 1.5: If DEBUG is set to False, all responses will be an 500 Server Error unless you specify the ALLOWED_HOSTS setting in your project's settings.py".

Suggested solution 2: Whenever starting the server in DEBUG = False and ALLOWED_HOSTS = [], display a warning on the console (stderr) that no request will be served because of the empty ALLOWED_HOSTS setting.

[Carl Meyer]

This is definitely a problem. I think a mention in the tutorial is a good idea, but I don't think that's an adequate solution to the problem. (See https://code.djangoproject.com/ticket/20120#comment:3)

[Tim Graham]

Previously suggested in #19875