$ ./x.py clean
Updating only changed submodules
Submodules updated in 0.11 seconds
Traceback (most recent call last):
  File "./x.py", line 20, in <module>
    bootstrap.main()
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 850, in main
    bootstrap(help_triggered)
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 824, in bootstrap
    build.download_stage0()
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 359, in download_stage0
    self._download_stage0_helper(filename, pattern)
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 394, in _download_stage0_helper
    get("{}/{}".format(url, filename), tarball, verbose=self.verbose)
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 36, in get
    download(sha_path, sha_url, False, verbose)
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 69, in download
    _download(path, url, probably_big, verbose, True)
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 96, in _download
    exception=exception)
  File "/home/philip/rust/src/bootstrap/bootstrap.py", line 146, in run
    ret = subprocess.Popen(args, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 711, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1343, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory