_django_clear_outbox should clear mail.outbox instead of creating new list (#407)

Author: peterlauri

pytest_django/plugin.py

@@ -399,11 +399,11 @@ def teardown():
 
 
 @pytest.fixture(autouse=True, scope='function')
-def _django_clear_outbox():
+def _django_clear_outbox(django_test_environment):
     """Clear the django outbox, internal to pytest-django."""
     if django_settings_is_configured():
         from django.core import mail
-        mail.outbox = []
+        del mail.outbox[:]
 
 
 @pytest.fixture(autouse=True, scope='function')