Remove unused imports and fix some other linter errors.

recipe_engine/bundle.py

 #!/usr/bin/env python
 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Bundles a universe_view into a standalone folder.
 
 This captures the result of doing all the network operations that recipe_engine
 might do at startup.
 """
 
 from __future__ import absolute_import
 import errno
 import logging
 import os
 import io
-import re
 import shutil
 import stat
 import subprocess
 import sys
-import types
 
 LOGGER = logging.getLogger(__name__)
 
 def prepare_destination(destination):
   LOGGER.info('prepping destination %s', destination)
   destination = os.path.abspath(destination)
   if os.path.exists(destination):
     LOGGER.fatal(
       'directory %s already exists! The directory must not exist to use it as '
       'a bundle target.', destination)
@@ skipping 86 matching lines @@
       will be tuned to run commands using this package.
     universe (loader.RecipeUniverse) - All of the recipes necessary to support
       root_package.
     destination (str) - Path to the bundle output folder. This folder should not
       exist before calling this function.
   """
   destination = prepare_destination(destination)
   for pkg in universe.packages:
     export_package(pkg, destination)
   prep_recipes_py(universe, root_package, destination)