new_contents: #!/usr/bin/env python
  
  # Copyright 2018 The Kubernetes Authors.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  # Need to figure out why this only fails on travis
  # pylint: disable=bad-continuation
  
  """Prepares for nested docker, and executes a command."""
  # TODO(Q-Lee): check the necessity of this once MountPropagation is available in
  # prow: https://github.com/kubernetes/kubernetes/pull/59252
  
  import argparse
  import os
  import subprocess
  import sys
  
  def check(*cmd):
      """Log and run the command, raising on errors."""
      print >>sys.stderr, 'Run:', cmd
      subprocess.check_call(cmd)
  
  
  def main(envs, cmd):
      """Make important mounts r-shared, then run script and verify it exits 0."""
      check("mount", "--make-rshared", "/lib/modules")
      check("mount", "--make-rshared", "/sys")
  
      for env in envs:
          key, val = env.split('=', 1)
          print >>sys.stderr, '%s=%s' % (key, val)
          os.environ[key] = val
      if not cmd:
          raise ValueError(cmd)
      check(*cmd)
  
  
  if __name__ == '__main__':
      PARSER = argparse.ArgumentParser()
      PARSER.add_argument('--env', default=[], action='append')
      PARSER.add_argument('cmd', nargs=1)
      PARSER.add_argument('args', nargs='*')
      ARGS = PARSER.parse_args()
      main(ARGS.env, ARGS.cmd + ARGS.args)
  
subject: Add a scenario to initiliaze nested dind