this line causes noise in the test suite, but if we just ignore it,
we'll never get to the bottom of it. It seems to only happen when
running 'iptest js', and *not* when running the 'casperjs test' command
directly, with a notebookserver that was launched manually.
this method wasn't currently working, and though we should put a working
method there as a utility, it isn't strictly necessary, since the whole
directory will be deleted
Paul Ivanov