old_contents: PREVIOUS_VERSION = '0.20.4'
  
  
  def main():
      print PREVIOUS_VERSION
  
  
  if __name__ == "__main__":
      main()
  
  
new_contents: from __future__ import print_function
  
  PREVIOUS_VERSION = '0.21.0'
  
  
  def main():
      print(PREVIOUS_VERSION)
  
  
  if __name__ == "__main__":
      main()
  
  
subject: Update version [skip ci]