Several change to mailman-web image.

- Download source code as zip from gitlab instead of git+https because speed.
- Check if the $DATABASE_URL is not defined, use a default sqlite database.
- Use dj-database-url package to set database in django settings using
  DATABASE_URL environment variable.
- Use UWSGI_LOG_URL as the URL for UWSGI logging and set it to a default value
  if it has not been defined.

web/mailman-web/settings.py

@@ -141,30 +141,8 @@ WSGI_APPLICATION = 'wsgi.application'
 # Database
 # https://docs.djangoproject.com/en/1.8/ref/settings/#databases
 
-DATABASES = {
-    #'default': {
-        # Use 'sqlite3', 'postgresql_psycopg2', 'mysql', 'sqlite3' or 'oracle'.
-        #'ENGINE': 'django.db.backends.sqlite3',
-        # DB name or path to database file if using sqlite3.
-        #'NAME': '/opt/mailman-web-data/mailmansuite.db',
-        # The following settings are not used with sqlite3:
-        #'USER': 'mailmansuite',
-        #'PASSWORD': 'mmpass',
-        # HOST: empty for localhost through domain sockets or '127.0.0.1' for
-        # localhost through TCP.
-        #'HOST': '',
-        # PORT: set to empty string for default.
-        #'PORT': '',
-    #}
-    # Example for PostgreSQL (recommanded for production):
-    'default': {
-        'ENGINE': 'django.db.backends.postgresql_psycopg2',
-        'NAME': 'mailmandb',
-        'USER': 'mailman',
-        'PASSWORD': 'mailmanpass',
-        'HOST': 'database',
-    }
-}
+
+DATABASES['default'] = dj-database-url.config(conn_max_age=600)
 
 
 # If you're behind a proxy, use the X-Forwarded-Host header