tests: vary dbname on each test run (#84947)

testsettings.py

@@ -1,14 +1,17 @@
 import os
+import secrets
 
 import django
 from django.conf import global_settings
 
+DB_NAME_PREFIX = 'test_mellon_'
+DB_NAME = DB_NAME_PREFIX + secrets.token_hex(63)[: 63 - len(DB_NAME_PREFIX)]
+
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.' + os.environ.get('DB_ENGINE', 'sqlite3'),
-        'NAME': 'mellon.sqlite3',
+        'ENGINE': 'django.db.backends.postgresql',
         'TEST': {
-            'NAME': 'mellon-test-' + os.environ.get('DB_ENGINE', 'sqlite3'),
+            'NAME': DB_NAME,
         },
     }
 }

tox.ini

@@ -9,7 +9,6 @@ setenv =
   DJANGO_SETTINGS_MODULE=testsettings
   PYTHONPATH=.
   SETUPTOOLS_USE_DISTUTILS=stdlib
-  DB_ENGINE=postgresql_psycopg2
   coverage: COVERAGE=--cov=mellon --cov-branch --cov-append --cov-report xml --cov-report html --cov-config .coveragerc
 usedevelop =
     coverage: true