Cannot run tests with the new changes on @master anymore

[Matthias Kestenholz]

I tried running the of Towel (​https://github.com/matthiask/towel/) with Django@master this morning. It does not really matter which project I'm taking though, none of them work right now.

For reference, the initial traceback:

mk@mbp:~/Projects/towel/tests$ .tox/py32-django17/bin/python manage.py runserver
Traceback (most recent call last):
  File "manage.py", line 13, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/core/management/__init__.py", line 427, in execute_from_command_line
    utility.execute()
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/core/management/__init__.py", line 419, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/core/management/__init__.py", line 287, in fetch_command
    commands = get_commands()
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/core/management/__init__.py", line 124, in get_commands
    apps.populate(installed_apps)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/apps/registry.py", line 87, in populate
    app_config.import_models(all_models)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/apps/base.py", line 160, in import_models
    self.models_module = import_module(models_module_name)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/__init__.py", line 124, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 821, in _gcd_import
    loader.load_module(name)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 436, in load_module
    return self._load_module(fullname)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 141, in decorated
    return fxn(self, module, *args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 342, in _load_module
    exec(code_object, module.__dict__)
  File "/Users/mk/Projects/towel/tests/testapp/models.py", line 9, in <module>
    from towel.modelview import ModelViewURLs
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 436, in load_module
    return self._load_module(fullname)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 141, in decorated
    return fxn(self, module, *args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/importlib/_bootstrap.py", line 342, in _load_module
    exec(code_object, module.__dict__)
  File "/Users/mk/Projects/towel/towel/modelview.py", line 24, in <module>
    class ModelView(object):
  File "/Users/mk/Projects/towel/towel/modelview.py", line 98, in ModelView
    _('The new object has been successfully created.')),
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/utils/translation/__init__.py", line 80, in ugettext
    return _trans.ugettext(message)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/utils/translation/trans_real.py", line 310, in gettext
    return do_translate(message, 'gettext')
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/utils/translation/trans_real.py", line 297, in do_translate
    _default = translation(settings.LANGUAGE_CODE)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/utils/translation/trans_real.py", line 199, in translation
    default_translation = _fetch(settings.LANGUAGE_CODE)
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/utils/translation/trans_real.py", line 182, in _fetch
    for app_config in reversed(list(apps.get_app_configs())):
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/apps/registry.py", line 108, in get_app_configs
    self.check_ready()
  File "/Users/mk/Projects/towel/tests/.tox/py32-django17/src/django/django/apps/registry.py", line 101, in check_ready
    "App registry isn't populated yet. "
RuntimeError: App registry isn't populated yet. Have you called django.setup()?

I could not get it running after several attempts of adding django.setup() to various places in manage.py and django/core/management/base.py

The code always hits populate(), ugettext(), get_app_configs(), check_ready, only the first few lines of the traceback are different.

[Marc Tamlyn]

I think you can fix this by using ugettext_lazy in place of ugettext which is certainly advisable for module-level code.

[Matthias Kestenholz]

Thanks. I was obviously looking in the wrong direction. You also found a bug in my code. Sorry for the noise!

[Marc Tamlyn]

Hmm, well the error message could be improved. For example I know that django.setup() is called by manage.py but you don't, and it wasn't obvious from the message that this was the issue.

[Aymeric Augustin]

It's a purposeful side-effect of the recent app-loading changes that revealed a bug in your code -- it's always wrong to call ugettext at import time.

That said, at the very least, we need to improve the error message. I suspect this exception is going to be encountered often. In practice it happens as soon as importing modules triggers a call to the app registry. Not using lazy translations will be the most common culprit, but looking up templates would have the same effect.

[Aymeric Augustin <aymeric.augustin@…>]

In f46603f8304a5b39c3b3064ec819587a78937113:

Fleshed out release notes for app loading.

Fixed #21715.

[Matthias Kestenholz]

Thanks, this is very helpful!