message: lldbtest.py: try to fix a runtime exception
  found on
diff: @@ -1219,12 +1219,15 @@ class Base(unittest2.TestCase):
  if os.path.isfile(src):
  dst = src.replace(self.log_basename, dst_log_basename)
  if os.name == "nt" and os.path.isfile(dst):
  - # On Windows, renaming a -> b will throw an exception if b exists. On non-Windows platforms
  - # it silently replaces the destination. Ultimately this means that atomic renames are not
  - # guaranteed to be possible on Windows, but we need this to work anyway, so just remove the
  - # destination first if it already exists.
  + # On Windows, renaming a -> b will throw an exception if
  + # b exists. On non-Windows platforms it silently
  + # replaces the destination. Ultimately this means that
  + # atomic renames are not guaranteed to be possible on
  + # Windows, but we need this to work anyway, so just
  + # remove the destination first if it already exists.
  remove_file(dst)
  + lldbutil.mkdir_p(os.path.dirname(dst))
  os.rename(src, dst)
  else:
  # success! (and we don't want log files) delete log files
  