message: Reinstate eager check inside _GradientsHelper
diff: @@ -542,6 +542,9 @@ def _GradientsHelper(ys,
  unconnected_gradients=UnconnectedGradients.NONE,
  src_graph=None):
  """Implementation of gradients()."""
  + if context.executing_eagerly():
  + raise RuntimeError("tf.gradients is not supported when eager execution "
  + "is enabled. Use tf.GradientTape instead.")
  if src_graph is None:
  src_graph = ops.get_default_graph()
  try:
  