Loads default extraction rules from the user and system extract.conf files.

        Returns None.

def load_defaults(self):
        '''
        Loads default extraction rules from the user and system extract.conf files.

        Returns None.
        '''
        # Load the user extract file first to ensure its rules take precedence.
        extract_files = [
            self.config.settings.user.extract,
            self.config.settings.system.extract,
        ]

        for extract_file in extract_files:
            if extract_file:
                try:
                    self.load_from_file(extract_file)
                except KeyboardInterrupt as e:
                    raise e
                except Exception as e:
                    if binwalk.core.common.DEBUG:
                        raise Exception("Extractor.load_defaults failed to load file '%s': %s" % (extract_file, str(e)))