code: def tox_configure(config):
      
      sections = config._cfg.sections
  
      # Cache these
      make_envconfig = None
      reader = None
  
      # Default to false so:
      # 1. we don't affect other projects using tox
      # 2. check migrations can happen gradually
      if str(sections.get('testenv', {}).get(STYLE_FLAG, 'false')).lower() == 'true':
          # Disable flake8 since we already include that
          config.envlist[:] = [env for env in config.envlist if not env.endswith('flake8')]
  
          make_envconfig = get_make_envconfig(make_envconfig)
          reader = get_reader(reader, config)
  
          add_style_checker(config, sections, make_envconfig, reader)
          add_style_formatter(config, sections, make_envconfig, reader)
docs: For more info, see: https://tox.readthedocs.io/en/latest/plugins.html
      For an example, see: https://github.com/tox-dev/tox-travis