Django flex sample: mysql -> postgres (#896)

* Changed Django Flex sample to use postgres

* small formatting change

* Added note about MySQL

Author: ryanmats

appengine/flexible/django_cloudsql/app.yaml

@@ -9,4 +9,3 @@ beta_settings:
 runtime_config:
   python_version: 3
 # [END runtime]
-

appengine/flexible/django_cloudsql/mysite/settings.py

@@ -81,7 +81,9 @@
 # [START dbconfig]
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.mysql',
+        # If you are using Cloud SQL for MySQL rather than PostgreSQL, set
+        # 'ENGINE': 'django.db.backends.mysql' instead of the following.
+        'ENGINE': 'django.db.backends.postgresql',
         'NAME': 'polls',
         'USER': '<your-database-user>',
         'PASSWORD': '<your-database-password>',

appengine/flexible/django_cloudsql/requirements.txt

@@ -2,3 +2,4 @@ Django==1.11
 mysqlclient==1.3.10
 wheel==0.29.0
 gunicorn==19.7.1
+psycopg2==2.7.1