'Add ``fname`` in a checklist for the filestore garbage collection.'

def _mark_for_gc(self, fname):

    full_path = os.path.join(self._full_path('checklist'), fname)
    if (not os.path.exists(full_path)):
        dirname = os.path.dirname(full_path)
        if (not os.path.isdir(dirname)):
            with tools.ignore(OSError):
                os.makedirs(dirname)
        open(full_path, 'ab').close()
