update python-flask-example-heroku materials

python-flask-example-heroku/.gitignore

 venv
+__pycache__
\ No newline at end of file

python-flask-example-heroku/app.py

@@ -2,9 +2,11 @@ import os
 from flask import Flask
 
 app = Flask(__name__)
-app.config.from_object(os.getenv("APP_SETTINGS", "config.DevelopmentConfig"))
+env_config = os.getenv("APP_SETTINGS", "config.DevelopmentConfig")
+app.config.from_object(env_config)
 
 
 @app.route("/")
 def index():
-    return f"The configured secret key is {app.config.get('SECRET_KEY')}"
+    secret_key = app.config.get("SECRET_KEY")
+    return f"The configured secret key is {secret_key}."

python-flask-example-heroku/config.py

 import os
 
 
-class Config(object):
+class Config:
     DEBUG = False
-    TESTING = False
-    SECRET_KEY = os.getenv("SECRET_KEY", "this-is-read-from-env")
+    DEVELOPMENT = False
+    SECRET_KEY = os.getenv("SECRET_KEY", "this-is-the-default-key")
 
 
 class ProductionConfig(Config):
-    DEBUG = False
+    pass
 
 
 class StagingConfig(Config):
-    DEVELOPMENT = True
     DEBUG = True
 
 
 class DevelopmentConfig(Config):
-    DEVELOPMENT = True
     DEBUG = True
+    DEVELOPMENT = True