old_contents: from os import getenv
  
  class Config(object):
      API_KEY = getenv('API_KEY')
      DAEMON_SLEEP_INTERVAL = 6 # hours
      MAIL_DEBUG = False
      MAIL_DEFAULT_SENDER = getenv('SENDER_EMAIL', 'dynamite@example.com')
      MAIL_PASSWORD = getenv('MAILGUN_SMTP_PASSWORD', None)
      MAIL_PORT = getenv('MAILGUN_SMTP_PORT', 25)
      MAIL_SERVER = getenv('MAILGUN_SMTP_SERVER', 'localhost')
      MAIL_USERNAME = getenv('MAILGUN_SMTP_LOGIN', None)
      MAIL_USE_SSL = False
      NOTIFY_EMAIL = getenv('NOTIFY_EMAIL', 'dynamite@example.com')
      SQLALCHEMY_DATABASE_URI = getenv('DATABASE_URL').replace('mysql2:', 'mysql:')
  
  class ProductionConfig(Config):
      DEBUG = False
      TESTING = False
  
  class DevelopmentConfig(Config):
      DEBUG = True
      MAIL_DEBUG = True
      SQLALCHEMY_DATABASE_URI = 'sqlite:///app.db'
  
  class TestingConfig(Config):
      TESTING = True
  
new_contents: from os import getenv
  
  class Config(object):
      API_KEY = getenv('API_KEY')
      DAEMON_SLEEP_INTERVAL = 6 # hours
      MAIL_DEBUG = False
      MAIL_DEFAULT_SENDER = getenv('SENDER_EMAIL', 'dynamite@example.com')
      MAIL_PASSWORD = getenv('MAILGUN_SMTP_PASSWORD', None)
      MAIL_PORT = getenv('MAILGUN_SMTP_PORT', 25)
      MAIL_SERVER = getenv('MAILGUN_SMTP_SERVER', 'localhost')
      MAIL_USERNAME = getenv('MAILGUN_SMTP_LOGIN', None)
      MAIL_USE_SSL = False
      NOTIFY_EMAIL = getenv('NOTIFY_EMAIL', 'dynamite@example.com')
      SQLALCHEMY_DATABASE_URI = getenv('DATABASE_URL', 'sqlite:///app.db').replace('mysql2:', 'mysql:')
  
  class ProductionConfig(Config):
      DEBUG = False
      TESTING = False
  
  class DevelopmentConfig(Config):
      DEBUG = True
      MAIL_DEBUG = True
  
  class TestingConfig(Config):
      TESTING = True
  
subject: Simplify default database setting, but allow it to be overridden