shutil recipe_module: port chromium_utils rmtree implementation.

recipe_modules/shutil/api.py

 # 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.
 
 from recipe_engine import recipe_api
 
 class ShutilApi(recipe_api.RecipeApi):
   def rmtree(self, path, **kwargs):
     name = kwargs.pop('name', 'rmtree %s' % path)
+    if kwargs.pop('flag_smart_rmtree', False):
+      # TODO(tandrii): remove this flag and makes this the only implementation.
+      self.m.python(
+          name,
+          self.resource('rmtree.py'),
+          args=[path],
+          **kwargs)
+      return
     self.m.python.inline(
         name,
         """
           import shutil, sys
           shutil.rmtree(sys.argv[1])
         """,
         args=[path],
         **kwargs)
 
   def copy(self, name, source, dest, step_test_data=None, **kwargs):
@@ skipping 114 matching lines @@
       if not os.path.isdir(path):
         if os.path.exists(path):
           print "%s exists but is not a dir" % path
           sys.exit(1)
         os.makedirs(path, mode)
       """,
       args=[path, str(mode)],
       **kwargs
     )
     self.m.path.mock_add_paths(path)