def is_readable_gs_handle(gs_handle):
  try:
    with files.open(gs_handle) as bak_file:
      bak_file.read(1)
  except files.PermissionDeniedError:
    return False
  return True
Clear any cached formats.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/datastore_admin/backup_handler.py/is_readable_gs_handle--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/utils/formats.py/reset_format_cache