Using @admin.register causes failure when AdminModel constructor is overriden

[Diego Andrés Sanabria Martín]

When trying to override the ModelAdmin constructor using the decorator @admin.register I get an exception.

This is an example for a new project called "what" with an simple app "why":

Commands to create the files (I used django 1.8.4):

django-admin stratproject what
cd what
python manage.py startapp why

what/settings.py

...
INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'why',
)
...

why/models.py

from django.db import models

# Create your models here.
class WhyMe(models.Model):
    name = models.CharField(max_length=255)

why/admin.py

from django.contrib import admin

from why.models import WhyMe

@admin.register(WhyMe)
class WhyMeAdmin(admin.ModelAdmin):
    def __init__(self, *args, **kwargs):
        super(WhyMeAdmin, self).__init__(*args, **kwargs)
        print("Whaaaaatttt???")

If I run the command 'runserver' I've got:

nhandled exception in thread started by <function wrapper at 0x10ae3b758>
Traceback (most recent call last):
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/core/management/commands/runserver.py", line 113, in inner_run
    autoreload.raise_last_exception()
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/utils/autoreload.py", line 249, in raise_last_exception
    six.reraise(*_exception)
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/apps/registry.py", line 115, in populate
    app_config.ready()
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/contrib/admin/apps.py", line 23, in ready
    self.module.autodiscover()
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/contrib/admin/__init__.py", line 26, in autodiscover
    autodiscover_modules('admin', register_to=site)
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/utils/module_loading.py", line 50, in autodiscover_modules
    import_module('%s.%s' % (app_config.name, module_to_search))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/diegueus9/.virtualenvs/django1.8/what/why/admin.py", line 6, in <module>
    class WhyMeAdmin(admin.ModelAdmin):
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/contrib/admin/decorators.py", line 28, in _model_admin_wrapper
    admin_site.register(models, admin_class=admin_class)
  File "/Users/diegueus9/.virtualenvs/django1.8/lib/python2.7/site-packages/django/contrib/admin/sites.py", line 108, in register
    admin_obj = admin_class(model, self)
  File "/Users/diegueus9/.virtualenvs/django1.8/what/why/admin.py", line 8, in __init__
    super(WhyMeAdmin, self).__init__(*args, **kwargs)
NameError: global name 'WhyMeAdmin' is not defined

However, if I use the normal registration 'admin.site.register(WhyMe, WhyMeAdmin)' everything works fine.
This also happens with latest 1.8.x, 1.9.x and 1.10.x.

Also I noticed that the print statement is executed twice and I'm not sure why and if that is another bug.

[Tim Graham]

It's a documented limitation: #24323.