code: protected function getSeverity($errorCode)
      {
          if (isset($this->severityMapping[$errorCode])) {
              return $this->severityMapping[$errorCode];
          } else {
              return $this->severityMapping[Logger::ERROR];
          }
      }
docs: Returns the Bugsnag severiry from a monolog error code.
  @param int $errorCode - one of the Logger:: constants.
  @return string