tox: provide postgresql test venvs (#43916)

tests/settings.py

@@ -1,5 +1,9 @@
-DATABASES['default']['TEST'] = {
-    'NAME': 'test-db.sqlite3',
+DATABASES = {
+    'default': {
+        'ENGINE': os.environ.get('DB_ENGINE', 'django.db.backends.sqlite3'),
+        'NAME': 'combo-test-%s' % os.environ.get(
+                "BRANCH_NAME", "").replace('/', '-')[:63]
+    }
 }
 
 LANGUAGE_CODE = 'en-us'

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/combo/{env:BRANCH_NAME:}
-envlist = coverage-py3-django111-pylint,py3-django22
+envlist = coverage-py3-django111-pylint-{sqlite,pg},py3-django22-pg
 
 [testenv]
 usedevelop = True
@@ -9,6 +9,9 @@ setenv =
   COMBO_SETTINGS_FILE=tests/settings.py
   TOX_WORK_DIR={toxworkdir}
   coverage: COVERAGE=--cov-report xml --cov-report html --cov=combo/
+  pg: DB_ENGINE=django.db.backends.postgresql_psycopg2
+passenv =
+  BRANCH_NAME
 deps =
   django111: django>=1.11,<1.12
   django22: django>=2.2,<2.3
@@ -23,7 +26,7 @@ deps =
   pylint<1.8
   pylint-django<0.8.1
   django-webtest<1.9.3
-  psycopg2
+  pg: psycopg2-binary
   django-mellon>=1.13
   quixote>=3.0
   vobject