Jenkinsfile: use pg_virtualenv to isolate the postgres database (#74887)

Jenkinsfile

@@ -5,7 +5,7 @@ pipeline {
     stages {
         stage('Unit Tests') {
             steps {
-                sh 'tox -rv'
+                sh 'pg_virtualenv -o fsync=off tox -rv'
             }
             post {
                 always {

tests/settings.py

@@ -0,0 +1,8 @@
+import os
+
+from zoo.settings import *
+
+# integrate with pg_virtualenv by getting pg configuration from environment variables
+for key in ('PGPORT', 'PGHOST', 'PGUSER', 'PGPASSWORD'):
+    if key in os.environ:
+        DATABASES['default'][key[2:]] = os.environ[key]

tox.ini

@@ -10,8 +10,10 @@ envlist =
   py3-dj32
 
 [testenv]
+passenv=
+  PG*
 setenv =
-  DJANGO_SETTINGS_MODULE=zoo.settings
+  DJANGO_SETTINGS_MODULE=tests.settings
   SETUPTOOLS_USE_DISTUTILS=stdlib
   JUNIT={tty::--junitxml=junit-{envname}.xml}
   COVERAGE={tty::--cov-report xml --cov-report html --cov=zoo/}