Handle heroku legacy-style postgres URIs

Author: bookernath

app.py

@@ -20,7 +20,7 @@
 app.config['APP_CLIENT_ID'] = os.getenv('APP_CLIENT_ID')
 app.config['APP_CLIENT_SECRET'] = os.getenv('APP_CLIENT_SECRET')
 app.config['SESSION_SECRET'] = os.getenv('SESSION_SECRET', os.urandom(64))
-app.config['SQLALCHEMY_DATABASE_URI'] = os.getenv('DATABASE_URL', 'sqlite:///data/hello_world.sqlite')
+app.config['SQLALCHEMY_DATABASE_URI'] = os.getenv('DATABASE_URL', 'sqlite:///data/hello_world.sqlite').replace("postgres://", "postgresql://", 1)
 app.config['SQLALCHEMY_ECHO'] = app.config['DEBUG']
 
 # Setup secure cookie secret