message: [lldbtestsuite] Don't crash on `None` input for is_exe().
  Now the function returns `False`, and the caller can take the
  appropriate action (in this case, for --executable, reporting
  that the file doesn't exist).
diff: @@ -51,6 +51,8 @@ from ..support import seven
  def is_exe(fpath):
  """Returns true if fpath is an executable."""
  + if fpath == None:
  + return False
  return os.path.isfile(fpath) and os.access(fpath, os.X_OK)
  