old_contents: import sys
  import os
  
  os.environ['DJANGO_SETTINGS_MODULE'] = 'django_mailbox.tests.settings'
  
  from django.core import management
  
  if len(sys.argv) > 1 and sys.argv[1] == 'test':
      management.execute_from_command_line()
      sys.exit()
new_contents: #!/usr/bin/env python
  import os
  import sys
  
  if __name__ == "__main__":
      os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings.local")
  
      from django.core.management import execute_from_command_line
  
      execute_from_command_line(sys.argv)
  
subject: Update manage.py to Python3 compatibility