message: [XLA:Python] vlog reason for backend initialization failure.
  Usually these failures are expected, but when they're not, it's really nice to see the error message.
diff: @@ -113,16 +113,17 @@ def _get_local_backends():
  _local_backends = collections.OrderedDict()
  for name, factory in _local_backend_factories.items():
  - logging.vlog(2, "Initializing backend '%s'" % name)
  + logging.vlog(1, "Initializing backend '%s'" % name)
  try:
  backend = factory()
  - except RuntimeError:
  + except RuntimeError as err:
  if name == 'cpu':
  # We always expect CPU to initialize successfully.
  raise
  else:
  # If the backend isn't built into the binary, or if it has no devices,
  # we expect a RuntimeError.
  + logging.vlog(1, "Error initializing backend '%s': %s" % (name, err))
  continue
  _local_backends[name] = backend
  return _local_backends
  