Add propagate exceptions.

Author: jslvtr

section11/app.py

@@ -10,6 +10,7 @@
 app = Flask(__name__)
 app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///data.db'
 app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
+app.config['PROPAGATE_EXCEPTIONS'] = True
 api = Api(app)
 
 """