old_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  import os
  
  # Flask
  SECRET_KEY = os.urandom(32)
  
  # SQLAlchemy (DB)
  SQLALCHEMY_DATABASE_URI = 'mysql://localhost'
  
new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  import os
  
  # Flask
  SECRET_KEY = os.urandom(32)
  
  # SQLAlchemy (DB)
  SQLALCHEMY_DATABASE_URI = 'mysql://localhost'
  
  # Heartbeat
  HEARTBEAT_SECRET = (
      r'6\x1eg\xd4\x19\xde\xad\xc1x\x00+\xc9\x04~_`%\x'
      r'f0\x7fF\xd9\x0b=\x91J\xe5\x0b\xeb\xc1D\xcd\x8d'
  )
subject: Add heartbeat secret into config