old_contents: #!/usr/bin/env python
  import os
  os.environ['DJANGO_SETTINGS_MODULE'] = 'tests.settings'
  
  from django.core import management
  
  if __name__ == "__main__":
      management.execute_from_command_line()
  
new_contents: #!/usr/bin/env python3
  import os
  os.environ['DJANGO_SETTINGS_MODULE'] = 'tests.settings'
  
  from django.core import management
  
  if __name__ == "__main__":
      management.execute_from_command_line()
  
subject: Move manage.py to Python 3.x