Отключите boto, регистрирующийся, не изменяя boto файлы

You could try

import logging
logging.getLogger('boto').setLevel(logging.CRITICAL)

which will suppress all (other than CRITICAL) errors.

Boto uses logging configuration files (e.g. /etc/boto.cfg, ~/.boto) so see if you can configure it to your needs that way.

The set_file_logger call simply adds a user-defined file to the logging setup, so you can't use that to turn logging off.