Remove assertion in django_settings_is_configured

django.conf.settings.configured is not necessarily True, in case DSM
wasn't set during `pytest_load_initial_conftests`, but gets set in the
project's conftest (via `pytest_configure`).

Fixes pytest-dev#146

Author: blueyed

pytest_django/lazy_django.py

@@ -22,8 +22,6 @@ def django_settings_is_configured():
 
     # If DJANGO_SETTINGS_MODULE is defined at this point, Django is assumed to
     # always be loaded.
-    from django.conf import settings
-    assert settings.configured is True
     return True