Why isn't behave's documented manual integration with Django working?

I have a Django (1.10.2) project ("theproject") and some behave (0.4.0) features. I've been using behave-django. python manage.py behave works. However, PyCharm (which uses the behave executable rather than a Django management command) doesn't know how to run my features, so I'm attempting to use behave's documented "manual integration" with Django.

My entire features/environment.py:

import os
import django
from django.test.runner import DiscoverRunner
from django.test.testcases import LiveServerTestCase
from splinter.browser import Browser

os.environ["DJANGO_SETTINGS_MODULE"] = "theproject.settings"

def before_all(context):
    django.setup()
    context.test_runner = DiscoverRunner()
    context.test_runner.setup_test_environment()
    context.old_db_config = context.test_runner.setup_databases()
    context.browser = Browser('phantomjs')

    # When we're running with PhantomJS we need to specify the window size.
    # This is a workaround for an issue where PhantomJS cannot find elements
    # by text - see: https://github.com/angular/protractor/issues/585
    if context.browser.driver_name == 'PhantomJS':
        context.browser.driver.set_window_size(1280, 1024)

def before_scenario(context, _):
    context.test_case = LiveServerTestCase
    context.test_case.setUpClass()

def after_scenario(context, _):
    context.test_case.tearDownClass()
    del context.test_case

def after_all(context):
    context.test_runner.teardown_databases(context.old_db_config)
    context.test_runner.teardown_test_environment()

    context.browser.quit()
    del context.browser

Here's INSTALLED_APPS from theproject/setting.py in case it's helpful (I removed 'behave-django' for this experiment):

INSTALLED_APPS = [
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'django_extensions',
    'oauth2_provider',
    'push_notifications',
    'raven.contrib.django.raven_compat',
    'rest_framework',
    'app1.apps.App1Config',
    'app2',
    'django.contrib.admin'  # Must follow apps for apps' models to appear in admin UI
]

When I run behave I get

Exception AppRegistryNotReady: Apps aren't loaded yet.
Traceback (most recent call last):
  File "/usr/local/bin/behave", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python2.7/site-packages/behave/__main__.py", line 109, in main
    failed = runner.run()
  File "/usr/local/lib/python2.7/site-packages/behave/runner.py", line 672, in run
    return self.run_with_paths()
  File "/usr/local/lib/python2.7/site-packages/behave/runner.py", line 678, in run_with_paths
    self.load_step_definitions()
  File "/usr/local/lib/python2.7/site-packages/behave/runner.py", line 658, in load_step_definitions
    exec_file(os.path.join(path, name), step_module_globals)
  File "/usr/local/lib/python2.7/site-packages/behave/runner.py", line 304, in exec_file
    exec(code, globals, locals)
  File "features/steps/common.py", line 5, in <module>
    from django.contrib.auth.models import User
  File "/usr/local/lib/python2.7/site-packages/django/contrib/auth/models.py", line 4, in <module>
    from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
  File "/usr/local/lib/python2.7/site-packages/django/contrib/auth/base_user.py", line 52, in <module>
    class AbstractBaseUser(models.Model):
  File "/usr/local/lib/python2.7/site-packages/django/db/models/base.py", line 105, in __new__
    app_config = apps.get_containing_app_config(module)
  File "/usr/local/lib/python2.7/site-packages/django/apps/registry.py", line 237, in get_containing_app_config
    self.check_apps_ready()
  File "/usr/local/lib/python2.7/site-packages/django/apps/registry.py", line 124, in check_apps_ready
    raise AppRegistryNotReady("Apps aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

How can this way of integrating django and behave be made to work?

Something I tried that didn't work (or not completely): I moved django.setup() to the top level of environment.py, right after setting DJANGO_SETTINGS_MODULE. That fixes AppRegistryNotReady, but many scenarios fail with

IntegrityError: duplicate key value violates unique constraint "auth_user_username_key"
DETAIL:  Key (username)=(username) already exists.

Under behave-django a transaction was started before each scenario and rolled back afterwards; that seems not to be happening now. LiveServerTestCase extends TransactionTestCase, so I'm puzzled.

Solution

Your database changes won't be rolled back between scenarios (hence the IntegrityError). The database is only torn down in after_all(). Try moving all code into the before_scenario and after_scenario functions (see related docs).

The execution time of your tests will increase, but the tests will be isolated. And as a quick fix this makes them pass for now at least. Hints for cleaner solutions in the comments and alternative answers.