docs: def is_ec2_instance():
      """Try fetching instance metadata at 'curl http://169.254.169.254/latest/meta-data/'
      to see if host is on an ec2 instance"""
  
      # Note: this code assumes that docker containers running on ec2 instances
      # inherit instances metadata, which they do as of 2016-08-25
  
      global IS_EC2_INSTANCE
  
      if IS_EC2_INSTANCE != -1:
          # Returned the cached value
          return IS_EC2_INSTANCE
  
      s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
      s.settimeout(0.2)
      try:
          s.connect(("169.254.169.254", 80))
          IS_EC2_INSTANCE = 1
          return True
      except socket.timeout:
          IS_EC2_INSTANCE = 0
          return False
      except socket.error:
          IS_EC2_INSTANCE = 0
          return False