Make Postgres object global and configure DJango settings correctly.

pytest_django_testing_postgresql.py

+import os
+
 from dj_database_url import parse
 from django.conf import settings
 import pytest
 from testing.postgresql import Postgresql
 
+_POSTGRESQL = Postgresql()
+
 
 @pytest.hookimpl(tryfirst=True)
 def pytest_load_initial_conftests(early_config, parser, args):
-    _postgresql = Postgresql()
-    settings.configure(DATABASES={'default': parse(_postgresql.url())})
+    os.environ['DJANGO_SETTINGS_MODULE'] = early_config.getini('DJANGO_SETTINGS_MODULE')
+    settings.DATABASES['default'] = parse(_POSTGRESQL.url())