django 1.7 stderr exception

[brianmay]

Hello,

When running with Django 1.7 rc2 and Django wants to report warnings with the database model, it will generate the following error.

(sid)root@aquitard:/tmp/brian/tmpL9WhrO# kg-manage  celery status
Traceback (most recent call last):
  File "/usr/share/python-karaage/bin/kg-manage", line 7, in <module>
    management.execute_from_command_line()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.7/dist-packages/djcelery/management/commands/celery.py", line 22, in run_from_argv
    self.validate()
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 361, in validate
    return self.check(app_configs=app_configs, display_num_errors=display_num_errors)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 415, in check
    self.stderr.write(msg)
AttributeError: 'Command' object has no attribute 'stderr'

This problem will only happen if Django tries to report warnings, if there are no warnings, this will not occur.

As per the following ticket: https://code.djangoproject.com/ticket/23133 django-celery should not call self.validate(), that was a kludge required for earlier Django versions that now breaks Django 1.7.

Thanks

[Karmak23]

As you can see in my commit, the fix is easy. commenting the self.validate() calls allow celery to start correctly (and https://github.com/mher/flower too, via django-celery).

[brianmay]

I can confirm with @Karmak23 - this is basically the same fix that is in the Debian package.

http://anonscm.debian.org/viewvc/python-modules/packages/django-celery/trunk/debian/patches/remove_validate.patch?revision=30180&view=markup

[brianmay]

Should also mention that Django 1.7 is released and considered stable; without this change django-celery is broken.

[ask]

Hmm, well we can remove it again I guess, but lots of people had problems with models being unavailable when it was disabled

[jpeyret]

Hmmm, maybe this is a dumb suggestion, but... in commands/celery.py, why not set the missing stderr if it's not there? Worked for me.

from sys import stderr
....
class Command(CeleryCommand):
if self.requires_model_validation:
if not hasattr(self, "stderr"):
self.stderr = stderr
self.validate()

Mind you, I have not thought about the ramifications of celery being run as a daemon. Would setting self.stderr to one of the logging module's functions be more appropriate in that case?

[ask]

That should work, but not the best solution if you are supposed to be able to override this with a command-line option to manage.py.

It's not a problem for daemonization, because all that happens later, then again if Django 1.7 no longer requires model validation you don't have to change anything.