en-US/about_bolt_logging.help.txt

logging
  Bolt prints messages both to the console and to log files. Messages can
  either come from Bolt's 'outputter', which logs user-facing messages like
  progress and results, or from the 'logger', which logs warnings, errors, and
  log-structured output to log files. Both of these message streams are
  configurable.
   
  By default, Bolt logs to the console at 'warn' level and writes a log file to
  '<project>/bolt-debug.log' at 'debug' level. Unless you are running a plan,
  Bolt runs in verbose mode by default.
   
  To learn more about projects, see the 'project' guide.
 
Documentation
  https://pup.pt/bolt-logging