old_contents: #  Copy this file to config.py.
  SECRET_KEY = 'foo-bar-blah-some-numbers'  # see python UUID for more
  
new_contents: #  Copy this file to config.py.
  SECRET_KEY = 'foo-bar-blah-some-numbers'  # see python UUID for more
  MONGO_DBNAME = 'name of the database to use, defaults to "server"'
subject: Update variable